Chemical amplification, positive resist compositions

ABSTRACT

A chemical amplification, positive resist composition is provided comprising (A) a photoacid generator and (B) a resin which changes its solubility in an alkali developer under the action of acid and has substituents of the formula: Ph—(CH 2 ) n OCH(CH 2 CH 3 )— wherein Ph is phenyl and n=1 or 2. The composition has many advantages including improved focal latitude, improved resolution, minimized line width variation or shape degradation even on long-term PED, minimized defect left after coating, development and stripping, and improved pattern profile after development and is suited for microfabrication by any lithography, especially deep UV lithography.

[0001] This invention relates to chemical amplification, positive resistcompositions which are sensitive to such radiation as UV, deep UV,electron beams, x-rays, excimer laser beams, γ-rays, and synchrotronradiation and suitable for the microfabrication of integrated circuits.

BACKGROUND OF THE INVENTION

[0002] While a number of efforts are currently being made to achieve afiner pattern rule in the drive for higher integration and operatingspeeds in LSI devices, deep- ultraviolet lithography is thought to holdparticular promise as the next generation in microfabricationtechnology. Deep UV lithography enables micropatterning to a featuresize of 0.3 or 0.4 μm. One technology that has attracted a good deal ofattention recently utilizes as the deep UV light source a high-intensityKrF excimer laser, especially an ArF excimer laser featuring a shorterwavelength. There is a desire to have a resist material capable ofmicropatterning to a smaller feature size.

[0003] In this regard, the recently developed, acid- catalyzed, chemicalamplification type positive resist materials (see JP-B 2-27660 and JP-A63-27829) are expected to comply with the deep UV lithography because oftheir many advantages including high sensitivity, resolution and dryetching resistance.

[0004] On use of the chemical amplification type resist compositions,especially chemical amplification type, positive working resistcompositions, a resist film is formed by dissolving a resin having acidlabile groups as a binder and a compound capable of generating an acidupon exposure to radiation (to be referred to as photoacid generator) ina solvent, applying the resist solution onto a substrate (inclusive of astepped substrate) by a variety of methods, and evaporating off thesolvent optionally by heating. The resist film is then exposed toradiation, for example, deep UV through a mask of a predeterminedpattern. This is optionally followed by post-exposure baking (PEB) forpromoting acid-catalyzed reaction. The exposed resist film is developedwith an aqueous alkaline developer for removing the exposed area of theresist film, obtaining a positive pattern profile. The pattern profileof resist is then transferred to the substrate by dry or wet etching.Since the stepped substrate and the aligner used in device fabricationhave more or less errors, there is a desire to have a resist materialcapable of forming an accurate pattern even when the focal point issomewhat offset, i.e., having a wide depth of focus.

[0005] Several acid labile group-substituted resins are known suitablefor use in chemically amplified positive resist compositions. Includedare resins protected with t-butyl ester groups or t-butoxycarbonylgroups (JP-B 2-27660 referred to above), resins protected with1-ethoxyethyl groups (JP-A 5-249682 and JP-A 6-308437), and resinsprotected with t-butoxycarbonyl groups and 1-alkoxyethyl groups (JP-A8-123032). These chemically amplified resist compositions, however, havetheir own problems. A variety of difficulties arise on the practicalapplication of these compositions. Such problems include, for example,environmental stability, focal latitude, particle, and storagestability.

[0006] The environmental stability is generally divided into twocategories. One environmental stability is related to the deactivationof a photo-generated acid by an air-borne base above the resist film ora base beneath the resist film and on the substrate. This phenomenon isoften seen when a photoacid generator capable of generating an acidhaving a high acid strength is used. It is expected that this problem issolved by introducing into the resin acid labile groups which are moreeasy to cleavage by acid or by lowering or weakening the acid strengthof the photo- generated acid. The other environmental stability is thatwhen the period from exposure to post-exposure baking (PEB) isprolonged, which is known as post-exposure delay (PED), thephoto-generated acid diffuses in the resist film so that aciddeactivation may occur when the acid labile groups are less susceptibleto scission and acid decomposition may take place when the acid labilegroups are susceptible to scission, often inviting a change of thepattern profile in either case. For example, this often invites anarrowing or slimming of the line width in the unexposed area in thecase of chemical amplification type, positive working, resistcompositions having acid labile groups mainly of acetal type.

[0007] Of the above-referred protective groups, the t-butoxycarbonylgroups have poor environmental stability on the surface of resist filmor on the substrate (i.e., at the interface between the resist and thesubstrate). As a result, the pattern obtained can have an outwardextending top (T-top profile) or is not sharply defined at all.Alternatively, pattern footing and tapering are sometimes possible. Alsothe resolving power is too low to provide a finer pattern.

[0008] The use of 1-alkoxyethyl groups, which have a high resolvingpower, also has problems. As a result of PED, the pattern profile variesto narrow the line width in the unexposed area (slimming). When thefocal point is offset on a stepped substrate, the pattern on the maskcannot be accurately transferred to the resist film. Specifically,although a rectangular pattern is obtained on accurate focusing, anyoffsetting of the focal point results in the pattern top beingnoticeably reduced, failing to keep rectangularity. Then the depth offocus is of significance when it is desired to produce a finer pattern.If the depth of focus is narrow, it becomes impossible to form anaccurate pattern on a stepped substrate is difficult, and hence tofabricate microelectronic devices by relying on pattern transfer throughetching.

[0009] The inventors confirmed that the introduction of a cycloalkylgroup such as cyclohexyloxyethyl into an alkoxyethyl group is effectivefor improving the depth of focus. However, probably because of improvedlipophilic property, the adhesion at the pattern-substrate interfacebecomes poor, allowing pattern stripping. Formation of particle in theresist film after development is another problem.

[0010] Even when a resin having acid labile groups of at least two typessuch as t-butoxycarbonyl and 1-alkoxyalkyl groups is used in a resistcomposition, no satisfactory results are obtained with respect to theabove-described problems, especially resolution and focal latitude.

SUMMARY OF THE INVENTION

[0011] An object of the invention is to provide a chemicalamplification, positive resist composition having an improvedresolution, pattern profile and focal latitude and having eliminated theproblems of adhesion, peeling and defect.

[0012] We have found that when a resin which changes its solubility inan alkali developer under the action of acid and has substituents of thefollowing general formula (1) is used in combination with a photoacidgenerator, there is formulated a chemical amplification, positive resistcomposition which has an adequate resolution, pattern profile and focallatitude to enable micropatterning. The resulting resist pattern haseliminated the problems of adhesion, stripping, particle and the like.The resist composition is fully effective when processed by deep-UVlithography.

Ph—(CH₂)_(n)OCH(CH₂CH₃)—(1)

[0013] Herein Ph is phenyl and n is 1 or 2.

[0014] Particularly when the resin which changes its solubility in analkali developer under the action of acid is a polyhydroxystyrenederivative or hydroxystyrene-(meth)acrylic acid copolymer in which someof the hydrogen atoms on phenolic hydroxyl groups and/or carboxyl groupsare protected with substituents of formula (1), the above advantages arefurther enhanced. Better results are obtained upon processing by deep-UVlithography.

[0015] According to the invention, there is provided a chemicalamplification, positive resist composition comprising

[0016] (A) a photoacid generator and

[0017] (B) a resin which changes its solubility in an alkali developerunder the action of acid and has substituents of the following generalformula (1):

Ph—(CH₂)_(n)OCH(CH₂CH₃)—  (1)

[0018] wherein Ph is phenyl and n is 1 or 2.

[0019] In one preferred embodiment, the resin (B) is an alkali-solubleresin comprising units of the following formula (2) or (2′) wherein someor all of the hydrogen atoms on phenolic hydroxyl groups and/or carboxylgroups are protected with substituents of the formula (1).

[0020] Herein R⁴ is hydrogen or methyl, R⁵ is a straight, branched orcyclic alkyl group of 1 to 8 carbon atoms, x is 0 or a positive integer,y is a positive integer, satisfying x+y≦5, M and N are positive integerssatisfying 0<N/(M+N)≦0.5.

[0021] In another preferred embodiment, the resin (B) is a branched,alkali-soluble resin comprising units of the following formula (2″)wherein some of the hydrogen atoms on phenolic hydroxyl groups areprotected with substituents of the formula (1).

[0022] Herein R⁴, R⁵, x and y are as defined above, ZZ is a divalentorganic group selected from the group consisting of CH₂, CH(OH),CR⁵(OH), C═O, and C(OR⁵)(OH), or a trivalent organic group representedby —C(OH)═, E may be the same or different and is a positive integer, Kis a positive integer, satisfying 0.001≦K/(K+E)≦0.1, and XX is 1 or 2.

[0023] The resin (B) may further has acid labile groups. Specifically,the resin (B) further has acid labile groups which are selected fromamong groups of the following general formulae (4) to (7), tertiaryalkyl groups of 4 to 20 carbon atoms, trialkylsilyl groups in which eachalkyl moiety has 1 to 6 carbon atoms, and oxoalkyl groups of 4 to 20carbon atoms.

[0024] Herein R¹⁰ and R¹¹ each are hydrogen or a straight, branched orcyclic alkyl group of 1 to 18 carbon atoms, R¹² is a monovalenthydrocarbon group of 1 to 18 carbon atoms which may contain a heteroatom such as oxygen atom, a pair of R¹⁰ and R¹¹, R¹⁰ and R¹², or R¹¹ andR¹² may form a ring, each of R¹⁰, R¹¹ and R¹² is a straight or branchedalkylene group of 1 to 18 carbon atoms when they form a ring.

[0025] R¹³ is a tertiary alkyl group of 4 to 20 carbon atoms, atrialkylsilyl group in which each alkyl moiety has 1 to 6 carbon atoms,an oxoalkyl group of 4 to 20 carbon atoms, or a group of formula (4), zis an integer of 0 to 6.

[0026] R¹⁴ is a straight, branched or cyclic alkyl group of 1 to 8carbon atoms or a substituted or unsubstituted aryl group of 6 to 20carbon atoms, h is equal to 0 or 1, and i is equal to 0, 1, 2 or 3,satisfying 2h+i=2 or 3.

[0027] R¹⁵ is a straight, branched or cyclic alkyl group of 1 to 8carbon atoms or a substituted or unsubstituted aryl group of 6 to 20carbon atoms, R¹⁶ to R²⁵ are independently hydrogen or monovalenthydrocarbon groups of 1 to 15 carbon atoms which may contain a heteroatom, R¹⁶ to R²⁵, taken together, may form a ring, and each of R¹⁶ toR²⁵ represents a divalent hydrocarbon group of 1 to 15 carbon atomswhich may contain a hetero atom, when they form a ring, or two of R¹⁶ toR²⁵ which are attached to adjoining carbon atoms may bond togetherdirectly to form a double bond.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0028] Resin

[0029] The chemical amplification, positive resist composition of theinvention is defined as comprising (A) a photoacid generator and (B) aresin which changes its solubility in an alkali developer under theaction of acid and has substituents of the following general formula(1):

Ph—(CH₂)_(n)OCH(CH₂CH₃)—  (1)

[0030] wherein Ph is phenyl and n is 1 or 2.

[0031] The resin which changes its solubility in an alkali developerunder the action of acid and has substituents of formula (1) isdescribed in detail.

[0032] The type of the resin is not critical as long as it is analkali-soluble resin having phenolic hydroxyl groups and/or carboxylgroups in which some or all of the hydrogen atoms on phenolic hydroxylgroups and/or hydroxyl groups of carboxyl groups are substituted withsubstituents of formula (1).

[0033] The alkali-soluble resin having phenolic hydroxyl groups and/orcarboxyl groups embraces homopolymers and copolymers ofp-hydroxystyrene, m-hydroxystyrene, α-methyl-p-hydroxystyrene,4-hydroxy-2-methylstyrene, 4-hydroxy-3-methylstyrene, methacrylic acidand acrylic acid, copolymers having carboxylic acid derivatives,diphenyl ethylene and analogues introduced at the terminus of theforegoing polymers, and branched copolymers based on a combination of ahydroxystyrene derivative monomer (as mentioned just above) with abranching monomer such as chloromethylstyrene.

[0034] Also included are copolymers obtained by introducing units freeof an alkali-soluble site (e.g., styrene, α-methylstyrene, acrylates,methacrylates, hydrogenated hydroxystyrene, maleic anhydride, andmaleimide) in addition to the above-mentioned units in such a proportionthat the solubility of the copolymer in an alkali developer is notextremely lowered. The acrylates and methacrylates used herein have anysubstituents which do not undergo acidolysis. Illustrative substituentsare straight, branched or cyclic alkyl groups of 1 to 8 carbon atoms andaromatic groups such as aryl groups, though not limited thereto.

[0035] Illustrative examples of the alkali-soluble resin, though notlimited thereto, include poly(p-hydroxystyrene), poly(m-hydroxystyrene),poly(4-hydroxy-2-methylstyrene), poly(4-hydroxy-3-methylstyrene),poly(α-methyl-p-hydroxystyrene), partially hydrogenatedpoly(p-hydroxystyrene) copolymers,p-hydroxystyrene/α-methyl-p-hydroxystyrene copolymers,p-hydroxystyrene/α-methylstyrene copolymers, p-hydroxystyrene/styrenecopolymers, p-hydroxystyrene/m-hydroxystyrene copolymers,p-hydroxystyrene/styrene copolymers, p-hydroxystyrene/acrylic acidcopolymers, p-hydroxystyrene/methacrylic acid copolymers,p-hydroxystyrene/methyl acrylate copolymers, p-hydroxystyrene/acrylicacid/methyl methacrylate copolymers, p-hydroxystyrene/methylmethacrylate copolymers, p-hydroxystyrene/methacrylic acid/methylmethacrylate copolymers, polymethacrylic acid, polyacrylic acid, acrylicacid/methyl acrylate copolymers, methacrylic acid/methyl methacrylatecopolymers, acrylic acid/maleimide copolymers, methacrylicacid/maleimide copolymers, p-hydroxystyrene/acrylic acid/maleimidecopolymers, and p-hydroxystyrene/methacrylic acid/maleimide copolymers,as well as dendritic polymers and hyperbranched polymers of theforegoing phenol derivatives.

[0036] Of these polymers, poly(p-hydroxystyrene), partially hydrogenatedpoly(p-hydroxystyrene) copolymers, p-hydroxystyrene/styrene copolymers,p-hydroxystyrene/acrylic acid copolymers, p-hydroxystyrene/methacrylicacid copolymers, and dendritic or hyperbranched polymers ofpoly(p-hydroxystyrene) are preferred.

[0037] Especially, alkali-soluble resins comprising units of thefollowing formula (2), (2′) or (2″) are preferred.

[0038] In the formulas, R⁴ is hydrogen or methyl. R⁵ is a straight,branched or cyclic alkyl group of 1 to 8 carbon atoms. Subscript x is 0or a positive integer, and y is a positive integer, satisfying x+y≦5. Mand N are positive integers satisfying 0<N/(M+N)≦0.5. ZZ is a divalentorganic group selected from among CH₂, CH(OH), CR⁵(OH), C═O, and C(OR⁵)(OH), or a trivalent organic group represented by —C(OH)═. E, which maybe the same or different, is a positive integer, and K is a positiveinteger, satisfying 0.001≦K/(K+E)≦0.1. XX is 1 or 2.

[0039] These alkali-soluble resins should preferably have a weightaverage molecular weight (Mw) of about 3,000 to about 100,000. Polymerswith a Mw of less than 3,000 may perform poorly and have low heatresistance and an insufficient film forming ability. With Mw beyond100,000, polymers may become less soluble in developers and resistsolvents. The dispersity or polydispersity index (Mw/Mn) of the resinshould preferably be up to 3.5, and more preferably up to 1.5. Polymerswith a dispersity of more than 3.5 often have poor resolution.

[0040] It is not critical how to prepare the polymer. In the case ofpoly(p-hydroxystyrene) and similar polymers, living anion polymerizationis recommended because a polymer having a low or narrow dispersity canbe synthesized.

[0041] The dendritic or hyperbranched polymer of phenol derivativerepresented by formula (2″) can be synthesized by effecting living anionpolymerization of a polymerizable monomer such as 4-tert-butoxystyreneand reacting a branching monomer such as chloromethylstyrene asappropriate during the living anion polymerization.

[0042] More particularly, living anion polymerization is started using apolymerizable monomer such as 4-tert-butoxystyrene. After apredetermined amount has been polymerized, a branching monomer such aschloromethylstyrene is introduced and reacted with the intermediate.Then the polymerizable monomer such as 4-tert-butoxystyrene and/or thebranching monomer such as chloromethylstyrene is added again forpolymerization. This operation is repeated many times until a desireddendritic or hyperbranched polymer is obtained. If necessary, theprotective groups used to enable living polymerization are deblocked,yielding a dendritic or hyperbranched polymer of phenol derivative.

[0043] Examples of the branching monomer are given below.

[0044] R⁴, R⁵, x and y are as defined above.

[0045] Illustrative examples of the dendritic or hyperbranched polymerare those having recurring units of the following approximate formulas(8) to (12).

[0046] Herein, broken lines represent polymer chains of the phenolderivative monomer, and D represents units based on the branchingmonomer. The number of broken line segments between D and D is depictedmerely for the sake of convenience, independent of the number ofrecurring units in the polymer chain included between D and D.

[0047] The dendritic or hyperbranched polymer of a phenol derivative isprepared by effecting living polymerization of the phenol derivative,reacting with a compound having a polymerizable moiety and a terminatingmoiety and proceeding further polymerization. By repeating thisoperation desired times, a dendritic or hyperbranched polymer of phenolderivative can be synthesized. The living polymerization may be effectedby any desired technique although living anion polymerization ispreferred because of ease of control.

[0048] For living anion polymerization to take place, the reactionsolvent is preferably selected from toluene, benzene, tetrahydrofuran,dioxane, and diethyl ether. Of these, polar solvents such astetrahydrofuran, dioxane, and diethyl ether are preferable. They may beused alone or in admixture of two or more.

[0049] The initiator used herein is preferably selected from sec-butyllithium, n-butyl lithium, naphthalene sodium and cumyl potassium. Theamount of the initiator used is proportional to the design molecularweight.

[0050] Preferred reaction conditions include a temperature of −80° C. to100° C., preferably −70° C. to 0° C., and a time of about 0.1 to 50hours, preferably about 0.5 to 5 hours.

[0051] One exemplary reaction scheme using sec-butyl lithium as theinitiator and 4-chloromethylstyrene as the branching monomer is shownbelow. The branching coefficient can be altered by repeating thereaction step any desired times.

[0052] Herein, R⁴, R⁵, x and y are as defined above, m₁ and m₂ each are0 or a positive integer, and R is a substituent capable of withstandingliving anion polymerization.

[0053] The living polymer thus obtained is deactivated or stopped, andthe substituent R which has been introduced for the progress of livinganion polymerization is deprotected, obtaining an alkali-soluble resin.

[0054] While the resin capable of changing its solubility in an alkalideveloper under the action of acid (B) which is formulated in thechemical amplification positive resist composition has substituents ofthe formula (1), the proportion of substituents (1) in the resin ispreferably about 1 to 40 mol% based on the phenolic hydroxyl groupsand/or carboxyl groups in the starting alkali-soluble resin. Theproportion of substituents (1) is more preferably about 5 to 30 mol %,and most preferably about 10 to 25 mol %. If the proportion ofsubstituents (1) is more than 40 mol %, there may often arise problemswith respect to resist solubility and particle. A proportion ofsubstituents (1) less than 1 mol % may often fail to exert the effectsof the invention.

[0055] More illustrative examples are polymers comprising recurringunits of the above formula (2) or (2″) wherein the hydrogen atoms onphenolic hydroxyl groups are replaced by substituents of the aboveformula (1) in a proportion of more than 1 mol % to 40 mol %, onaverage, based on the entire hydrogen atoms on phenolic hydroxyl groups,the polymers having a weight average molecular weight of about 3,000 toabout 100,000.

[0056] Alternatively, polymers comprising recurring units of the aboveformula (2′), specifically copolymers comprising p-hydroxystyrene and/orα-methyl-p-hydroxystyrene and acrylic acid and/or methacrylic acid, areuseful wherein the hydrogen atoms on carboxyl groups in the acrylic acidand/or methacrylic acid are replaced by substituents of the aboveformula (1) or other acid labile groups, and units based on acrylateand/or methacrylate are present in the polymer in a proportion from morethan 1 mol % to 40 mol % on average, and some of the hydrogen atoms onphenolic hydroxyl groups in the p-hydroxystyrene and/ora-methyl-p-hydroxystyrene may be replaced by substituents of the aboveformula (1). More preferably, the units based on acrylate and/ormethacrylate and the units based on p-hydroxystyrene and/orα-methyl-p-hydroxystyrene having substituents of formula (1) are presentin the polymer in a total proportion from more than 1 molt to 40 molt onaverage.

[0057] Such polymers are exemplified by those polymers comprisingrecurring units of the following general formula (2a), (2a′) or (2a″)and having a weight average molecular weight of about 3,000 to about100,000.

[0058] In the formulas, R⁴ is hydrogen or methyl. R⁵ is a straight,branched or cyclic alkyl group of 1 to 8 carbon atoms. R⁶ is asubstituent of the above formula (1). R^(6a) is hydrogen or asubstituent of formula (1) and/or an acid labile group, and at leastsome, preferably all, of the R^(6a) groups are substituents of formula(1) and/or acid labile groups. Subscript x is 0 or a positive integer,and y is a positive integer, satisfying x+y<≦5. S and T are positiveintegers, satisfying 0.01≦S/(S+T)≦0.4. The R⁶ groups may be the same ordifferent when y is 2 or more. M and N are positive integers, and L is 0or a positive integer, satisfying 0<N/(M+N)≦0.4 and0.01≦(N+L)/(M+N+L)≦0.4. ZZ is a divalent organic group selected fromamong CH₂, CH(OH), CR⁵(OH), C═O, and C(OR⁵)(OH), or a trivalent organicgroup represented by —C(OH)═. K is a positive integer, satisfying0.001≦K/(K+S+T)≦0.1. XX is 1 or 2. The acid labile groups will bedescribed later.

[0059] Examples of the straight, branched or cyclic alkyl group of 1 to8 carbon atoms represented by R⁵ include methyl, ethyl, propyl,isopropyl, n-butyl, isobutyl, tert-butyl, cyclohexyl and cyclopentyl.

[0060] As compared with conventional resins based on linear polymers,the resin which changes its solubility in an alkali developer under theaction of acid, obtained by introducing substituents of formula (1) intothe dendritic or hyperbranched polymer, has the advantage that theperformance of chemical amplification positive resist compositions isimproved due to the effects of polymer branching and increased freevolume.

[0061] The advantages inherent to the invention are derived byintroducing substituents of formula (1) into an alkali-soluble resinwhile the resist performance is dictated by the properties of theoriginal alkali-soluble resin prior to substitution. Therefore, theoriginal alkali-soluble resin should be selected in accordance with thedesired properties.

[0062] For example, the dendritic or hyperbranched polymers have asmaller molecular size than linear polymers, which leads to an improvedresolution. When it is desired to improve heat resistance by increasingthe molecular weight of the polymer, this can be accomplished withoutincreasing the viscosity, which leads to an improved process stability.The dendritic polymers have an increased number of terminuses, which iseffective for improving adhesion to substrates.

[0063] It is believed that these advantages are due to the effects ofentanglement between polymers. It is believed that polymers are not keptseparate, but form a cluster. In the case of greater or strongerclusters, their size or strength affects the resolution and edgeroughness. It is understood that a linear polymer increases the degreeof entanglement in proportion to the backbone length and forms a greateror stronger cluster. By contrast, the dendritic or hyperbranched polymergives rise to the entanglement of polymer segments corresponding to thelength of branches, independent of the overall length of the polymer,and as a consequence, the likelihood of entanglement between polymersthemselves is retarded. This leads to the advantages of improvedresolution, minimized increase of viscosity even in the case of highmolecular weight one, and improved adhesion.

[0064] The resin which changes its solubility in an alkali developerunder the action of acid, obtained by introducing substituents offormula (1) into the dendritic or hyperbranched polymer, preferably hasa weight average molecular weight of about 5,000 to about 100,000 and anumber of branches of 0.001 to 0.1, based on the entire monomer unitsconstituting the polymer.

[0065] For the synthesis of the resin which changes its solubility in analkali developer under the action of acid and has substituents offormula (1), preferably phenolic hydroxyl groups and/or carboxyl groupsin the alkali-soluble resin are reacted with a propenyl ether such asbenzyl propenyl ether or phenethyl propenyl ether under acidicconditions. Also preferably, synthesis is carried out by reacting thealkali-soluble resin with benzyl or phenethyl 1-halogenated propyl ethersuch as benzyl 1-chloropropyl ether, benzyl 1-bromopropyl ether,phenethyl 1-chloropropyl ether or phenethyl 1-bromopropyl ether underbasic conditions.

[0066] The propenyl ethers can be synthesized in a conventional waywhile referring to Greene, “Protective Groups in Organic Synthesis,”John Wiley & Sons, 1981. Specifically, benzyl alcohol or 2-phenethylalcohol is reacted with allyl chloride or allyl bromide under basicconditions to form an allyl ether. Alternatively, benzyl chloride or2-phenethyl chloride is reacted with allyl alcohol under basicconditions to form an allyl ether. Next, the allyl ether is isomerizedthrough rearrangement into a propenyl ether. Further, hydrogen chlorideor hydrogen bromide is added to the propenyl ether to form a benzyl orphenethyl halogenated propyl ether.

[0067] In the formulas, Ph is phenyl, n is as defined above, and X ischlorine, bromine or iodine.

[0068] While the resin capable of changing its solubility in an alkalideveloper under the action of acid (B) which is formulated in thechemical amplification positive resist composition has substituents ofthe formula (1), it may further have acid labile groups of one or moretypes. The total of substituents of formula (1) and other acid labilegroups is preferably 1 to 80 mol % based on the phenolic hydroxyl groupsand/or carboxyl groups in the original alkali-soluble resin. This totalis more preferably 5 to 50 mol %, and most preferably 10 to 40 mol %.

[0069] Provided that the proportion of substituents of formula (1)relative to the phenolic hydroxyl groups and/or carboxyl groups in thealkali-soluble resin is A mol % and the proportion of other acid labilegroups relative to the phenolic hydroxyl groups and/or carboxyl groupsis B mol %, it is recommended that A/(A+B) range from 0.1 to 1, morepreferably from 0.3 to 1, and most preferably from 0.5 to 1.

[0070] The acid labile groups other than formula (1) are preferablygroups of the following general formulae (4) to (7), tertiary alkylgroups of 4 to 20 carbon atoms, preferably 4 to 15 carbon atoms,trialkylsilyl groups whose alkyl groups each have 1 to 6 carbon atoms,or oxoalkyl groups of 4 to 20 carbon atoms.

[0071] Herein R¹⁰ and R¹¹ are independently hydrogen or straight,branched or cyclic alkyl groups of 1 to 18 carbon atoms, preferably 1 to10 carbon atoms, for example, methyl, ethyl, propyl, isopropyl, n-butyl,sec-butyl, tert-butyl, cyclopentyl, cyclohexyl, 2-ethylhexyl andn-octyl. R¹² is a monovalent hydrocarbon group of 1 to 18 carbon atoms,preferably 1 to 10 carbon atoms, which may have a hetero atom (e.g.,oxygen atom), for example, straight, branched or cyclic alkyl groups,and such groups in which some hydrogen atoms are replaced by hydroxyl,alkoxy, oxo, amino or alkylamino groups. Illustrative examples of thesubstituted alkyl groups are given below.

[0072] A pair of R¹⁰ and R¹¹, a pair of R¹⁰ and R¹², or a pair of R¹¹and R¹², taken together, may form a ring. Each of R¹⁰, R¹¹ and R¹² is astraight or branched alkylene group of 1 to 18 carbon atoms, preferably1 to 10 carbon atoms, when they form a ring.

[0073] R¹³ is a tertiary alkyl group of 4 to 20 carbon atoms, preferably4 to 15 carbon atoms, a trialkylsilyl group whose alkyl groups each have1 to 6 carbon atoms, an oxoalkyl group of 4 to 20 carbon atoms or agroup of formula (4). Exemplary tertiary alkyl groups are tert-butyl,tert-amyl, 1,1-diethylpropyl, 1-methylcyclopentyl, 1-ethylcyclopentyl,1-isopropylcyclopentyl, 1-butylcyclopentyl, 1-methylcyclohexyl,1-ethylcyclohexyl, 1-isopropylcyclohexyl, 1-butylcyclohexyl,1-ethyl-2-cyclopentenyl, 1-ethyl-2-cyclohexenyl, and2-methyl-2-adamantyl. Exemplary trialkylsilyl groups are trimethylsilyl,triethylsilyl, and dimethyl-tert-butylsilyl. Exemplary oxoalkyl groupsare 3-oxocyclohexyl, 4-methyl-2-oxooxan-4-yl, and5-methyl-5-oxooxoran-4-yl. Letter z is an integer of 0 to 6.

[0074] R14 is a straight, branched or cyclic alkyl group of 1 to 8carbon atoms or substituted or unsubstituted aryl group of 6 to 20carbon atoms. Exemplary straight, branched or cyclic alkyl groupsinclude methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl,tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl, cyclohexyl,cyclopentylmethyl, cyclopentylethyl, cyclohexylmethyl andcyclohexylethyl. Exemplary substituted or unsubstituted aryl groupsinclude phenyl, methylphenyl, naphthyl, anthryl, phenanthryl, andpyrenyl. Letter h is equal to 0 or 1, i is equal to 0, 1, 2 or 3,satisfying 2h+i=2 or 3.

[0075] R¹⁵ is a straight, branched or cyclic alkyl group of 1 to 8carbon atoms or substituted or unsubstituted aryl group of 6 to 20carbon atoms, examples of which are as exemplified for R¹⁴. R¹⁶ to R²⁵are independently hydrogen or monovalent hydrocarbon groups of 1 to 15carbon atoms which may contain a hetero atom, for example, straight,branched or cyclic alkyl groups such as methyl, ethyl, propyl,isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl,n-octyl, n-nonyl, n-decyl, cyclopentyl, cyclohexyl, cyclopentylmethyl,cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl,and cyclohexylbutyl, and substituted ones of these groups in which somehydrogen atoms are replaced by hydroxyl, alkoxy, carboxy,alkoxycarbonyl, oxo, amino, alkylamino, cyano, mercapto, alkylthio, andsulfo groups. R¹⁶ to R²⁵, for example, a pair of R¹⁶ and R¹⁷, a pair ofR¹⁶ and R¹⁸, a pair of R¹⁷ and R¹⁹, a pair of R¹⁸ and R¹⁹, a pair of R²⁰and R²¹, or a pair of R²² and R²³, taken together, may form a ring. WhenR¹⁶ to R²⁶ form a ring, they are divalent hydrocarbon groups which maycontain a hetero atom, examples of which are the above-exemplifiedmonovalent hydrocarbon groups with one hydrogen atom eliminated. Also,two of R¹⁶ to R²⁵ which are attached to adjacent carbon atoms (forexample, a pair of R¹⁶ and R¹⁸, a pair of R¹⁸ and R²⁴ , or a pair of R²²and R²⁴ ) may directly bond together to form a double bond.

[0076] Of the acid labile groups of formula (4), illustrative examplesof the straight or branched groups are given below.

CH₂—O—CH₃ —CH₂—O—CH₂—CH₃ —CH₂—O—(CH₂)₂—CH₃

[0077] Of the acid labile groups of formula (4), illustrative examplesof the cyclic groups include tetrahydrofuran-2-yl,2-methyltetrahydrofuran-2-yl, tetrahydropyran-2-yl and2-methyltetrahydropyran-2-yl.

[0078] Illustrative examples of the acid labile groups of formula (5)include tert-butoxycarbonyl, tert-butoxy-carbonylmethyl,tert-amyloxycarbonyl, tert-amyloxycarbonyl-methyl,1,1-diethylpropyloxycarbonyl, 1,1-diethylpropyloxycarbonylmethyl,1-ethylcyclopentyl-oxycarbonyl, 1-ethylcyclopentyloxycarbonylmethyl,1-ethyl-2-cyclopentenyloxycarbonyl,1-ethyl-2-cyclopentenyl-oxycarbonylmethyl, 1-ethoxyethoxycarbonylmethyl,2-tetrahydropyranyloxycarbonylmethyl, and2-tetrahydro-furanyloxycarbonylmethyl.

[0079] Illustrative examples of the acid labile groups of formula (6)include 1-methylcyclopentyl, 1-ethylcyclopentyl, 1-n-propylcyclopentyl,1-isopropylcyclopentyl, 1-n-butylcyclopentyl, 1-sec-butylcyclopentyl,1-methylcyclohexyl, 1-ethylcyclohexyl, 3-methyl-1-cyclopenten-3-yl,3-ethyl-1-cyclopenten-3-yl, 3-methyl-1-cyclohexen-3-yl, and3-ethyl-1-cyclohexen-3-yl.

[0080] Illustrative examples of the acid labile groups of formula (7)are given below.

[0081] Exemplary of the tertiary alkyl group of 4 to 20 carbon atoms,preferably 4 to 15 carbon atoms, are tert-butyl, tert-amyl,3-ethyl-3-pentyl and dimethylbenzyl.

[0082] Exemplary of the trialkylsilyl groups whose alkyl groups eachhave 1 to 6 carbon atoms are trimethylsilyl, triethylsilyl, andtert-butyldimethylsilyl.

[0083] Exemplary of the oxoalkyl groups of 4 to 20 carbon atoms are3-oxocyclohexyl and groups represented by the following formulae.

[0084] In an alternative embodiment, the resin capable of changing itssolubility in an alkali developer under the action of acid and havingsubstituents of the formula (1) is a polymer comprising units of formula(2) or (2′) in which some of the hydrogen atoms on phenolic hydroxylgroups are crosslinked within a molecule and/or between molecules in aproportion of more than 0 mol % to 50 mol %, on the average, of theentire phenolic hydroxyl groups in the polymer, with crosslinking groupshaving C—O—C linkages represented by the following general formula (3a)or (3b).

[0085] The crosslinking groups having C—O—C linkages may be groupsrepresented by the following general formula (3a) or (3b), preferablythe following general formula (3a′) or (3b′).

[0086] Herein, each of R⁷ and R⁸ is hydrogen or a straight, branched orcyclic alkyl group of 1 to 8 carbon atoms, or R⁷ and R⁸, taken together,may form a ring, and each of R⁷ and R⁸ is a straight or branchedalkylene group of 1 to 8 carbon atoms when they form a ring. R⁹ is astraight, branched or cyclic alkylene group of 1 to 10 carbon atoms,letter b is 0 or an integer of 1 to 10. A is an a-valent aliphatic oralicyclic saturated hydrocarbon group, aromatic hydrocarbon group orheterocyclic group of 1 to 50 carbon atoms, which may be separated by ahetero atom and in which some of the hydrogen atom attached to carbonatoms may be replaced by hydroxyl, carboxyl, carbonyl or halogen. B is—CO—O—, —NHCO—O— or —NHCONH—. Letter a is an integer of 2 to 8 and a isan integer of 1 to 7.

[0087] Herein, each of R⁷ and R⁸ is hydrogen or a straight, branched orcyclic alkyl group of 1 to 8 carbon atoms, or R⁷ and R⁸, taken together,may form a ring, and each of R⁷ and R⁸ is a straight or branchedalkylene group of 1 to 8 carbon atoms when they form a ring. R⁹ is astraight, branched or cyclic alkylene group of 1 to 10 carbon atoms,letter b is 0 or an integer of 1 to 5. A is an a″-valent straight,branched or cyclic alkylene, alkyltriyl or alkyltetrayl group of 1 to 20carbon atoms or arylene group of 6 to 30 carbon atoms, which may beseparated by a hetero atom and in which some of the hydrogen atomattached to carbon atoms may be replaced by hydroxyl, carboxyl, acyl orhalogen. B is —CO—O—, —NHCO—O— or —NHCONH—. Letter a″ is an integer of 2to 4 and a′″ is an integer of 1 to 3.

[0088] Examples of the straight, branched or cyclic C₁₋₈ alkyl grouprepresented by R⁷ and R⁸ are as exemplified for R⁵.

[0089] Examples of the straight, branched or cyclic C₁₋₁₀ alkylene grouprepresented by R⁹ include methylene, ethylene, propylene, isopropylene,n-butylene, isobutylene, cyclohexylene, and cyclopentylene.

[0090] Exemplary halogen atoms are fluorine, chlorine, bromine andiodine.

[0091] Illustrative examples of A are described later. Thesecrosslinking groups of formulae (3a) and (3b) originate from alkenylether compounds and halogenated alkyl ether compounds to be describedlater.

[0092] As understood from the value of a′ in formula (3a) or (3b), thecrosslinking group is not limited to a divalent one and trivalent tooctavalent groups are acceptable. For example, the divalent crosslinkinggroup is exemplified by groups of the following formulas (3a″) and(3b″), and the trivalent crosslinking group is exemplified by groups ofthe following formulas (3a′″) and (3b′″).

[0093] R⁷, R⁸, R⁹, A, B and b are as defined above.

[0094] In a further alternative embodiment, the resin capable ofchanging its solubility in an alkali developer under the action of acidand having substituents of the formula (1) is a polymer comprisingrecurring units of the following general formula (2b), (2b′) or (2b″),and more preferably the same polymer in which hydrogen atoms on phenolichydroxyl groups represented by R are eliminated to leave oxygen atomswhich are crosslinked within a molecule and/or between molecules withcrosslinking groups having C—O—C linkages represented by the aboveformula (3a) or (3b).

[0095] Herein, R represents an acid labile group, attached to an oxygenatom, other than the substituent of formula (1) or a crosslinking grouphaving C-O-C linkages, attached to an oxygen atom, represented by theabove formula (3a) or (3b). R⁴ is hydrogen or methyl, R⁵ is a straight,branched or cyclic alkyl group of 1 to 8 carbon atoms. R¹³ is a tertiaryalkyl group of 4 to 20 carbon atoms, an aryl-substituted alkyl group of7 to 20 carbon atoms, an oxoalkyl group of 4 to 20 carbon atoms or agroup represented by —CR¹⁰R¹¹OR¹². R¹⁰ and R¹¹ are independentlyhydrogen or straight, branched or cyclic alkyl groups of 1 to 18 carbonatoms, R¹² is a monovalent hydrocarbon group of 1 to 18 carbon atomswhich may have a hetero atom, or R¹⁰ and R¹¹, R¹⁰ and R¹², or R¹″ andR¹², taken together, may form a ring, with the proviso that each of R¹⁰,R¹¹ and R¹² is a straight or branched alkylene group of 1 to 18 carbonatoms when they form a ring. Letter zz is an integer of 0 to 6. S1 is apositive number, each of S2, T1, and T2 is 0 or a positive number,satisfying 0≦T1/(S1+T1+T2+S2)≦0.8, 0.01≦S1/(S1+T1+T2+S2)≦0.4,0≦T2/(S1+T1+T2+S2)≦0.09, and 0.01≦(S1+S2)/(S1+T1+T2+S2) ≦0.8. Each of uand w is 0 or a positive integer, and v is a positive integer,satisfying u+v+w≦5. Letters m, x and y are as defined above.

[0096] More preferably, S1, S2, T1 and T2 satisfy the ranges:0≦T1/(S1+T1+T2+S2)≦0.3, 0.05≦S1/(S1+T1+T2+S2)≦0.3,0≦S2/(S1+T1+T2+S2)≦0.3, 0.5≦T2/(S1+T1+T2+S2)≦0.95, and0.05≦(S1+S2)/(S1+T1+T2+S2)≦0.5; and most preferably,0≦T1/(S1+T1+T2+S2)≦0.15, 0.1≦S1/(S1+T1+T2+S2)≦0.25,0≦S2/(S1+T1+T2+S2)≦0.15, 0.5≦T2/(S1+T1+T2+S2)≦0.9, and0.1≦(S1+S2)/(S1+T1+T2+S2)≦0.4.

[0097] Herein, R represents an acid labile group, attached to an oxygenatom, other than the substituent of formula (1) or a crosslinking grouphaving C—O—C linkages, attached to an oxygen atom, represented by theabove formula (3a) or (3b). R⁴ is hydrogen or methyl, R⁵ is a straight,branched or cyclic alkyl group of 1 to 8 carbon atoms. R^(6a) ishydrogen, a substituent of formula (1) or an acid labile group asmentioned above, and at least some, preferably all of the R^(6a) groupsare acid labile groups. R¹³ is a tertiary alkyl group of 4 to 20 carbonatoms, an aryl-substituted alkyl group of 7 to 20 carbon atoms, anoxoalkyl group of 4 to 20 carbon atoms or a group represented by—CR¹⁰R¹¹OR¹². R¹⁰ and R¹¹ are independently hydrogen or straight,branched or cyclic alkyl groups of 1 to 18 carbon atoms, R¹² is amonovalent hydrocarbon group of 1 to 18 carbon atoms which may have ahetero atom, or R¹⁰ and R¹¹, R¹⁰ and R¹², or R¹¹ and R¹², takentogether, may form a ring, with the proviso that each of R¹⁰, R¹¹ andR¹² is a straight or branched alkylene group of 1 to 18 carbon atomswhen they form a ring. Letter z is an integer of 0 to 6. Letters n, u,w, v, x and y are as defined above.

[0098] N is a positive number, each of M1, M2, M3 and M4 is 0 or apositive number, satisfying 0<N/(M1+M2+M3+M4+N)≦0.4,0.01≦(M3+N)/(M1+M2+M3+M4+N)≦0.5, 0≦M2/(M1+M2+M3+M4+N)≦0.99, andM1+M2+M3+M4+N=1. M1, M3 and M4 are not equal to 0 at the same time. Morepreferably, N, M1, M2, M3 and M4 satisfy the ranges:0<N/(M1+M2+M3+M4+N)<0.3, 0.05≦(M3+N)/(M1+M2+M3+M4+N)≦0.4, and0.5≦M2/(M1+M2+M3+M4+N)≦0.95, and most preferably,0<N/(M1+M2+M3+M4+N)≦0.3, 0.1≦(M3+N)/(M1+M2+M3+M4+N)≦0.3, and0.6≦M2/(M1+M2+M3+M4+N)≦0.9.

[0099] In the formula, R, R⁴, R⁵, R³ R¹⁰ R¹, R¹² z, S, 2, T1, T2, u, w,v, n, x and y are as defined above. ZZ is a divalent organic groupselected from the group consisting of CH₂, CH(OH), CR⁵(OH), C═O, andC(OR⁵)(OH), or a trivalent organic group represented by —C(OH)═. XX is 1or 2. K is a positive integer satisfying 0.001≦K/(S1+T1+T2+S2+K)≦0.1.

[0100] In the embodiment wherein the resin (B) capable of changing itssolubility in an alkali developer under the action of acid and havingsubstituents of the formula (1) is crosslinked with acid labilesubstituents, specifically crosslinked within a molecule and/or betweenmolecules with crosslinking groups having C—O—C linkages resulting fromreaction of phenolic hydroxyl groups with an alkenyl ether compound orhalogenated alkyl ether, the proportion of crosslinking groups havingC—O—C linkages is preferably, on the average, from more than 0 mol % to20 mol %, more preferably from 0.2 mol % to 10 mol %. At 0 mol %, fewbenefits of the crosslinking group would be obtained, resulting in areduced contrast of alkali dissolution rate and a low resolution. Withmore than 20 mol %, a too much crosslinked polymer would gel, becomeinsoluble in alkali, induce a film thickness change, internal stressesor bubbles upon alkali development, and lose adhesion to the substratedue to less hydrophilic groups.

[0101] The total proportion of substituents of formula (1) and acidlabile groups is preferably, on the average, more than 0 mol % to 50 mol%, especially 10 to 40 mol %. At 0 mol %, there result a reducedcontrast of alkali dissolution rate and a low resolution. With more than50 mol %, the polymer may lose alkali solubility or affinity to analkali developer upon development and have poor resolution.

[0102] By properly selecting the proportions of crosslinking groupshaving C—O—C linkages and acid labile groups within the above-definedranges, it becomes possible to control the size and configuration of aresist pattern as desired. In the resist composition according to theinvention, the contents of crosslinking groups having C—O—C linkages andacid labile groups in the polymer have substantial influence on thedissolution rate contrast of a resist film and govern the properties ofthe resist composition relating to the size and configuration of aresist pattern.

[0103] Now A in the crosslinking group is described. The (a′+1)-valentorganic groups represented by A include hydrocarbon groups, for example,substituted or unsubstituted alkylene groups preferably having 1 to 50carbon atoms, and especially 1 to 40 carbon atoms, substituted orunsubstituted arylene groups preferably having 6 to 50 carbon atoms, andespecially 6 to 40 carbon atoms (these alkylene and arylene groups mayhave an intervening hetero atom or group such as O, NH, N(CH₃), S orSO₂, and where substituted, the substituents are hydroxyl, carboxyl,acyl and fluorine), and combinations of these alkylene groups with thesearylene groups, and a′-valent groups corresponding to the foregoinggroups from which a hydrogen atom attached to a carbon atom iseliminated (wherein a′ is an integer of 3 to 8). Additional examplesinclude (a′+1)-valent heterocyclic groups, and combinations of theseheterocyclic groups with the foregoing hydrocarbon groups.

[0104] Illustrative examples of A are given below.

[0105] Preferably, in formula (3a), R⁷ is methyl, R⁸ is hydrogen, b isequal to 0, and A is ethylene, 1,4-butylene or 1,4-cyclohexylene.

[0106] In preparing the polymer which is crosslinked within a molecularand/or between molecules with crosslinking groups having C—O—C linkages,synthesis can be made by reacting a corresponding non-crosslinkedpolymer with an alkenyl ether in the presence of an acid catalyst in aconventional manner.

[0107] Alternatively, where decomposition of other acid labile groupstakes place in the presence of an acid catalyst, the end product can besynthesized by first reacting an alkenyl ether with hydrochloric acid orthe like to form a halogenated alkyl ether, and reacting it with apolymer under basic conditions in a conventional manner.

[0108] Illustrative, non-limiting, examples of the alkenyl ether includeethylene glycol divinyl ether, triethylene glycol divinyl ether,1,2-propanediol divinyl ether, 1,3-propanediol divinyl ether,1,3-butanediol divinyl ether, 1,4-butanediol divinyl ether,tetramethylene glycol divinyl ether, neopentyl glycol divinyl ether,trimethylolpropane trivinyl ether, trimethylolethane trivinyl ether,hexanediol divinyl ether, 1,4-cyclohexanediol divinyl ether,1,4-divinyloxymethylcyclohexane, tetraethylene glycol divinyl ether,pentaerythritol divinyl ether, pentaerythritol trivinyl ether,pentaerythritol tetravinyl ether, sorbitol tetravinyl ether, sorbitolpentavinyl ether, ethylene glycol diethylene vinyl ether, triethyleneglycol diethylene vinyl ether, ethylene glycol dipropylene vinyl ether,triethylene glycol diethylene vinyl ether, trimethylolpropanetriethylene vinyl ether, trimethylolpropane diethylene vinyl ether,pentaerythritol diethylene vinyl ether, pantaerythritol triethylenevinyl ether, pentaerythritol tetraethylene vinyl ether, and thecompounds of the following formulae (I-1) through (I-31).

[0109] Also useful are terephthalic acid diethylene vinyl ether,phthalic acid diethylene vinyl ether, isophthalic acid diethylene vinylether, phthalic acid dipropylene vinyl ether, terephthalic aciddipropylene vinyl ether, isophthalic acid dipropylene vinyl ether,maleic acid diethylene vinyl ether, fumaric acid diethylene vinyl ether,itaconic acid diethylene vinyl ether as well as the compounds of thefollowing formulae (II-1) through (II-11). Useful alkenyl ethers are notlimited to these examples.

[0110] In the resist composition according to the invention, the resinused as component (B) is as described above. When the resin has acidlabile groups other than formula (1), the preferred acid labile groupsare 1-ethylcyclopentyl, 1-ethylcyclohexyloxycarbonylmethyl, tert-amyl,1-ethoxyethyl, 1-ethoxypropyl, tetrahydrofuranyl, tetrahydropyranyl,tert-butyl, 1-ethylcyclohexyl, tert-butoxycarbonyl,tert-butoxy-carbonylmethyl groups, and substituents of formula (3a)wherein R⁷ is methyl, R⁸ is hydrogen, b is equal to 0, and A isethylene, 1,4-butylene or 1,4-cyclohexylene.

[0111] In a single polymer, these substituents may be incorporated aloneor in admixture of two or more types. A blend of two or more polymershaving substituents of different types is also acceptable.

[0112] The percent proportion of these substituents substituting forphenol and carboxyl groups in the polymer is not critical. Preferablythe percent substitution is selected such that when a resist compositioncomprising the polymer is applied onto a substrate to form a coating,the unexposed area of the coating may have a dissolution rate of 0.01 to10 Å/sec in a 2.38% tetramethylammonium hydroxide (TMAH) developer.

[0113] On use of a polymer containing a greater proportion of carboxylgroups which can reduce the alkali dissolution rate, the percentsubstitution must be increased or non-acid- labile substituents to bedescribed later must be introduced.

[0114] When acid labile groups for intramolecular and/or intermolecularcrosslinking are to be introduced, the percent proportion ofcrosslinking substituents is preferably up to 20%, more preferably up to10%. If the percent substitution of crosslinking substituents is toohigh, crosslinking results in a higher molecular weight which canadversely affect dissolution, stability and resolution. It is alsopreferred to further introduce another non-crosslinking acid labilegroup into the crosslinked polymer at a percent substitution of up to10% for adjusting the dissolution rate to fall within the above range.

[0115] In the case of poly(p-hydroxystyrene), the optimum percentsubstitution differs between a substituent having a strong dissolutioninhibitory action such as a tert-butoxycarbonyl group and a substituenthaving a weak dissolution inhibitory action such as an acetal groupalthough the overall percent substitution is preferably 10 to 40%, morepreferably 20 to 30%.

[0116] Polymers having such acid labile groups introduced therein shouldpreferably have a weight average molecular weight (Mw) of about 3,000 toabout 100,000. With a Mw of less than 3,000, polymers would performpoorly and often lack heat resistance and film formability. Polymerswith a Mw of more than 100,000 would be less soluble in a developer anda resist solvent.

[0117] Where non-crosslinking acid labile groups are introduced, thepolymer should preferably have a dispersity (Mw/Mn) of up to 3.5,preferably up to 1.5. A polymer with a dispersity of more than 3.5 oftenresults in a low resolution. Where crosslinking acid labile groups areintroduced, the starting alkali-soluble resin should preferably have adispersity (Mw/Mn) of up to 1.5, and the dispersity is kept at 3 orlower even after protection with crosslinking acid labile groups. If thedispersity is higher than 3, dissolution, coating, storage stabilityand/or resolution is often poor.

[0118] To impart a certain function, suitable substituent groups may beintroduced into some of the phenolic hydroxyl and carboxyl groups on theacid labile group-protected polymer. Exemplary are substituent groupsfor improving adhesion to the substrate, non-acid-labile groups foradjusting dissolution in an alkali developer, and substituent groups forimproving etching resistance. Illustrative, non-limiting, substituentgroups include 2-hydroxyethyl, 2-hydroxypropyl, methoxymethyl,methoxycarbonyl, ethoxycarbonyl, methoxycarbonylmethyl,ethoxycarbonylmethyl, 4-methyl-2-oxo-4-oxoranyl,4-methyl-2-oxo-4-oxanyl, methyl, ethyl, propyl, n-butyl, sec-butyl,acetyl, pivaloyl, adamantyl, isobornyl, and cyclohexyl.

[0119] Photoacid Generator (A)

[0120] The photoacid generator (A) is a compound capable of generatingan acid upon exposure to high energy radiation. Preferred photoacidgenerators are sulfonium salts, iodonium salts, sulfonyldiazomethanes,and N-sulfonyloxyimides. These photoacid generators are illustratedbelow while they may be used alone or in admixture of two or more.

[0121] Sulfonium salts are salts of sulfonium cations with sulfonates.Exemplary sulfonium cations include triphenylsulfonium,(4-tert-butoxyphenyl)diphenylsulfonium,bis(4-tert-butoxyphenyl)phenylsulfonium,tris(4-tert-butoxyphenyl)sulfonium,(3-tert-butoxyphenyl)diphenyl-sulfonium,bis(3-tert-butoxyphenyl)phenylsulfonium,tris(3-tert-butoxyphenyl)sulfonium,(3,4-di-tert-butoxy-phenyl)diphenylsulfonium,bis(3,4-di-tert-butoxyphenyl)-phenylsulfonium,tris(3,4-di-tert-butoxyphenyl)sulfonium,diphenyl(4-thiophenoxyphenyl)sulfonium,(4-tert-butoxy-carbonylmethyloxyphenyl)diphenylsulfonium, tris(4-tert-butoxycarbonylmethyloxyphenyl)sulfonium,(4-tert-butoxyphenyl)bis(4-dimethylaminophenyl)sulfonium,tris(4-dimethylaminophenyl)sulfonium, 2-naphthyldiphenylsulfonium,dimethyl-2-naphthylsulfonium, 4-hydroxyphenyldimethylsulfonium,4-methoxyphenyldimethylsulfonium, trimethylsulfonium,2-oxocyclohexylcyclohexylmethylsulfonium, trinaphthylsulfonium, andtribenzylsulfonium. Exemplary sulfonates includetrifluoromethanesulfonate, nonafluorobutanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,4,4-toluenesulfonyloxybenzenesulfonate, naphthalenesulfonate,camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,butanesulfonate, and methanesulfonate. Sulfonium salts based oncombination of the foregoing examples are included.

[0122] Iodinium salts are salts of iodonium cations with sulfonates.Exemplary iodinium cations are aryliodonium cations includingdiphenyliodinium, bis(4-tert-butylphenyl)iodonium,4-tert-butoxyphenylphenyliodonium, and 4-methoxyphenylphenyliodonium.Exemplary sulfonates include trifluoromethanesulfonate,nonafluorobutanesulfonate, heptadecafluorooctanesulfonate,2,2,2-trifluoroethanesulfonate, pentafluorobenzenesulfonate,4-trifluoromethylbenzenesulfonate, 4-fluorobenzenesulfonate,toluenesulfonate, benzenesulfonate, 4,4-toluenesulfonyloxybenzenesulfonate, naphthalenesulfonate, camphorsulfonate,octanesulfonate, dodecylbenzenesulfonate, butanesulfonate, andmethanesulfonate. Iodonium salts based on combination of the foregoingexamples are included.

[0123] Preferred sulfonium salts are triphenylsulfonium10-camphorsulfonate, triphenylsulfonium nonafluorobutanesulfonate,triphenylsulfonium 4-(4-toluenesulfonyloxy)-benzenesulfonate,triphenylsulfonium 2-trifluoromethylbenzenesulfonate,4-tert-butoxyphenyldiphenylsulfonium 4-toluenesulfonate,4-tert-butoxyphenyldiphenylsulfonium 10-camphorsulfonate,4-tert-butoxyphenyldiphenylsulfonium pentafluorobenzenesulfonate,4-tert-butylphenyldiphenylsulfonium nonafluorobutanesulfonate,4-tert-butylphenyldiphenylsulfonium 4-toluenesulfonate,diphenyl-4-methylphenylsulfonium4-(4-toluenesulfonyloxy)benzenesulfonate,tris(4-tert-butylphenyl)sulfonium 10-camphorsulfonate,tris(4-tert-butylphenyl)sulfonium pentafluorobenzenesulfonate,tris(4-methylphenyl)sulfonium nonafluorobutanesulfonate,tris(4-methylphenyl)sulfonium heptadecaoctanesulfonate, anddiphenylmethylsulfonium nonafluorobutanesulfonate, though not limitedthereto. Preferred iodonium salts are bis(4-tert-butylphenyl)iodonium10-camphorsulfonate, bis(4-tert-butylphenyl)iodoniumnonafluorobutanesulfonate, bis(4-tert-butylphenyl)iodoniumpentafluorobenzenesulfonate, and bis(4-tert-butylphenyl)iodonium4-(4-toluenesulfonyloxy)-benzenesulfonate, though not limited thereto.

[0124] Exemplary sulfonyldiazomethane compounds includebissulfonyldiazomethane compounds and sulfonyl-carbonyldiazomethanecompounds such as bis(ethylsulfonyl)-diazomethane,bis(1-methylpropylsulfonyl)diazomethane,bis(2-methylpropylsulfonyl)diazomethane,bis(1,1-dimethylethylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)-diazomethane,bis(perfluoroisopropylsulfonyl)diazomethane,bis(phenylsulfonyl)diazomethane,bis(4-methylphenylsulfonyl)diazomethane,bis(2,4-dimethylphenylsulfonyl)diazomethane,bis(2-naphthylsulfonyl)-diazomethane,4-methylphenylsulfonylbenzoyldiazomethane,tert-butylcarbonyl-4-methylphenylsulfonyldiazomethane,2-naphthylsulfonylbenzoyldiazomethane,4-methylphenylsulfonyl-2-naphthoyldiazomethane,methylsulfonylbenzoyldiazomethane, andtert-butoxycarbonyl-4-methylphenylsulfonyldiazomethane.

[0125] N-sulfonyloxyimide photoacid generators include combinations ofimide skeletons with sulfonates. Exemplary imide skeletons aresuccinimide, naphthalene dicarboxylic acid imide, phthalimide,cyclohexyldicarboxylic acid imide, 5-norbornene-2,3-dicarboxylic acidimide, and 7-oxabicyclo[2.2.1]-5-heptene-2,3-dicarboxylic acid imide.Exemplary sulfonates include trifluoromethanesulfonate,nonafluorobutanesulfonate, heptadecafluorooctanesulfonate,2,2,2-trifluoroethanesulfonate, pentafluorobenzenesulfonate,4-trifluoromethylbenzenesulfonate, 4-fluorobenzenesulfonate,toluenesulfonate, benzenesulfonate, naphthalenesulfonate,camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,butanesulfonate, and methanesulfonate.

[0126] Benzoinsulfonate photoacid generators include benzoin tosylate,benzoin mesylate, and benzoin butanesulfonate.

[0127] Pyrogallol trisulfonate type photoacid generators includepyrogallol, phloroglucinol, catechol, resorcinol, hydroquinone, in whichall the hydroxyl groups are replaced by trifluoromethanesulfonate,nonafluorobutanesulfonate, heptadecafluorooctanesulfonate,2,2,2-trifluoroethanesulfonate, pentafluorobenzenesulfonate,4-trifluoromethylbenzenesulfonate, 4-fluorobenzenesulfonate,toluenesulfonate, benzenesulfonate, naphthalenesulfonate,camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,butanesulfonate, and methanesulfonate.

[0128] Nitrobenzyl sulfonate photoacid generators include2,4-dinitrobenzyl sulfonate, 2-nitrobenzyl sulfonate, and2,6-dinitrobenzyl sulfonate, with exemplary sulfonates includingtrifluoromethanesulfonate, nonafluorobutanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, and methanesulfonate. Alsouseful are analogous nitrobenzyl sulfonate compounds in which the nitrogroup on the benzyl side is replaced by a trifluoromethyl group.

[0129] Sulfone photoacid generators include bis(phenylsulfonyl)methane,bis(4-methylphenylsulfonyl)methane, bis(2-naphthylsulfonyl)methane,2,2-bis(phenylsulfonyl)propane, 2,2-bis(4-methylphenylsulfonyl)propane,2,2-bis(2-naphthylsulfonyl)propane,2-methyl-2-(p-toluenesulfonyl)propiophenone,2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane, and2,4-dimethyl-2-(p-toluenesulfonyl)pentan-3-one.

[0130] Photoacid generators in the form of glyoxime derivatives includebis-o-(p-toluenesulfonyl)-α-dimethylglyoxime,bis-o-(p-toluenesulfonyl)-α-diphenylglyoxime,bis-o-(p-toluenesulfonyl)-α-dicyclohexyl-glyoxime,bis-o-(p-toluenesulfonyl)-2,3-pentanedioneglyoxime,bis-o-(p-toluenesulfonyl)-2-methyl-3,4-pentanedioneglyoxime,bis-o-(n-butanesulfonyl)-α-dimethylglyoxime,bis-o-(n-butanesulfonyl)-α-diphenylglyoxime,bis-o-(n-butanesulfonyl)-α-dicyclohexylglyoxime,bis-o-(n-butane-sulfonyl)-2,3-pentanedioneglyoxime,bis-o-(n-butane-sulfonyl)-2-methyl-3,4-pentanedioneglyoxime,bis-o-(methanesulfonyl)-α-dimethylglyoxime,bis-o-(trifluoro-methanesulfonyl)-α-dimethylglyoxime,bis-o-(1,1,1-trifluoroethanesulfonyl)-α-dimethylglyoxime,bis-o-(tert-butanesulfonyl)-α-dimethylglyoxime,bis-o-(perfluoro-octanesulfonyl)-α-dimethylglyoxime,bis-o-(cyclohexyl-sulfonyl)-α-dimethylglyoxime,bis-o-(benzenesulfonyl)-α-dimethylglyoxime,bis-o-(p-fluorobenzenesulfonyl)-α-dimethylglyoxime,bis-o-(p-tert-butylbenzenesulfonyl)-α-dimethylglyoxime,bis-o-(xylenesulfonyl)-α-dimethylglyoxime, andbis-o-(camphorsulfonyl)-α-dimethylglyoxime.

[0131] Of these photoacid generators, the sulfonium salts,bissulfonyldiazomethane compounds, and N-sulfonyloxyimide compounds arepreferred.

[0132] While the anion of the optimum acid to be generated differsdepending on the ease of scission of acid labile groups introduced inthe polymer, an anion which is non-volatile and not extremely diffusiveis generally chosen. The preferred anions include benzenesulfonic acidanions, toluenesulfonic acid anions,4,4-toluenesulfonyloxybenzenesulfonic acid anions,pentafluorobenzenesulfonic acid anions, 2,2,2-trifluoroethanesulfonicacid anions, nonafluorobutanesulfonic acid anions,heptadecafluorooctanesulfonic acid anions, and camphorsulfonic acidanions.

[0133] In the chemically amplified positive resist composition, anappropriate amount of the photoacid generator (A) is from more than 0part to 20 parts, and especially 1 to 10 parts by weight per 100 partsby weight of the base resin in the composition. The photoacid generatorsmay be used alone or in admixture of two or more. The transmittance ofthe resist film can be controlled by using a photoacid generator havinga low transmittance at the exposure wavelength and adjusting the amountof the photoacid generator added.

[0134] Resist Composition

[0135] As defined above, the chemical amplification, positive resistcomposition of the invention is comprised of (A) the photoacid generatorand (B) the resin which changes its solubility in an alkali developerunder the action of acid and has substituents of formula (1).Illustrative embodiments of the invention are given below although theinvention is not limited thereto.

[0136] Embodiment 1 is a chemical amplification, positive resistcomposition comprising (A) the photoacid generator, (B) the resin whichchanges its solubility in an alkali developer under the action of acidand has substituents of formula (1), and (G) an organic solvent.

[0137] Embodiment 2 is a chemical amplification, positive resistcomposition as set forth as Embodiment 1 and further comprising (C) aresin which changes its solubility in an alkali developer under theaction of acid and is free of substituents of formula (1).

[0138] Embodiment 3 is a chemical amplification, positive resistcomposition as set forth as Embodiment 1 or 2 and further comprising (D)a basic compound.

[0139] Embodiment 4 is a chemical amplification, positive resistcomposition as set forth as Embodiment 1, 2 or 3 and further comprising(E) an organic acid derivative.

[0140] Embodiment 5 is a chemical amplification, positive resistcomposition as set forth as Embodiment 1, 2, 3 or 4 and furthercomprising (F) a compound with a molecular weight of up to 3,000 whichchanges its solubility in an alkali developer under the action of acid.

[0141] The respective components are described below.

[0142] Component (G)

[0143] Component (G) is an organic solvent. Illustrative, non-limiting,examples include butyl acetate, amyl acetate, cyclohexyl acetate,3-methoxybutyl acetate, methyl ethyl ketone, methyl amyl ketone,cyclohexanone, cyclopentanone, 3-ethoxyethyl propionate, 3-ethoxymethylpropionate, 3-methoxymethyl propionate, methyl acetoacetate, ethylacetoacetate, diacetone alcohol, methyl pyruvate, ethyl pyruvate,propylene glycol monomethyl ether, propylene glycol monoethyl ether,propylene glycol monomethyl ether propionate, propylene glycol monoethylether propionate, ethylene glycol monomethyl ether, ethylene glycolmonoethyl ether, diethylene glycol monomethyl ether, diethylene glycolmonoethyl ether, 3-methyl-3-methoxybutanol, N-methylpyrrolidone,dimethyl sulfoxide, y-butyrolactone, propylene glycol methyl etheracetate, propylene glycol ethyl ether acetate, propylene glycol propylether acetate, methyl lactate, ethyl lactate, propyl lactate, andtetramethylene sulfone. Of these, the propylene glycol alkyl etheracetates and alkyl lactates are especially preferred. The solvents maybe used alone or in admixture of two or more. An exemplary usefulsolvent mixture is a mixture of a propylene glycol alkyl ether acetateand an alkyl lactate. It is noted that the alkyl groups of the propyleneglycol alkyl ether acetates are preferably those of 1 to 4 carbon atoms,for example, methyl, ethyl and propyl, with methyl and ethyl beingespecially preferred. Since the propylene glycol alkyl ether acetatesinclude 1,2-and 1,3-substituted ones, each includes three isomersdepending on the combination of substituted positions, which may be usedalone or in admixture. It is also noted that the alkyl groups of thealkyl lactates are preferably those of 1 to 4 carbon atoms, for example,methyl, ethyl and propyl, with methyl and ethyl being especiallypreferred.

[0144] When the propylene glycol alkyl ether acetate is used as thesolvent, it preferably accounts for at least 50% by weight of the entiresolvent. Also when the alkyl lactate is used as the solvent, itpreferably accounts for at least 50% by weight of the entire solvent.When a mixture of propylene glycol alkyl ether acetate and alkyl lactateis used as the solvent, this mixture preferably accounts for at least50% by weight of the entire solvent. In this solvent mixture, it isfurther preferred that the propylene glycol alkyl ether acetate is 60 to95% by weight and the alkyl lactate is 40 to 5% by weight. A lowerproportion of the propylene glycol alkyl ether acetate would invite aproblem of inefficient coating whereas a higher proportion thereof wouldprovide insufficient dissolution and allow for particle and particleformation. A lower proportion of the alkyl lactate would provideinsufficient dissolution and cause the problem of many particles andparticle whereas a higher proportion thereof would lead to a compositionwhich has a too high viscosity to apply and loses storage stability.

[0145] Usually the solvent is used in amounts of about 300 to 2,000parts, preferably about 400 to 1,000 parts by weight per 100 parts byweight of the base resin in the chemically amplified positive resistcomposition. The concentration is not limited to this range as long asfilm formation by existing methods is possible.

[0146] Other Resin (C)

[0147] A resin which changes its solubility in an alkali developer underthe action of acid and is free of substituents of formula (1) may beadded as component (C) to the chemically amplified positive resistcomposition in addition to the resin (B) which changes its solubility inan alkali developer under the action of acid and has substituents offormula (1).

[0148] Though not critical, the resin (C) which changes its solubilityin an alkali developer under the action of acid and is free ofsubstituents of formula (1) is preferably selected from thosealkali-soluble resins as described previously in connection withcomponent (B) having introduced therein acid labile groups as describedabove in connection with component (B), for example, groups of the aboveformulas (4) to (7), tertiary alkyl groups with 4 to 20 carbon atoms,preferably with 4 to 15 carbon atoms, trialkylsilyl groups whose alkylgroups each have 1 to 6 carbon atoms, and oxoalkyl groups of 4 to 20carbon atoms.

[0149] Preferred are resins in the form of poly(p-hydroxystyrene) andp-hydroxystyrene/(meth)acrylic acid copolymers in which some of thehydrogen atoms on phenolic hydroxyl groups and/or carboxyl groups arereplaced by acid labile groups of one or more types.

[0150] Illustrative preferred acid labile groups are 1-akoxyalkyl,tert-alkyloxycarbonyl, tert-alkyl, 2-tetrahydropyranyl and2-tetrahydrofuranyl groups.

[0151] Preferred combinations of two or more types of acid labile groupsare combinations of different acetal groups, combinations of groupsdiffering in ease of cleavage under the action of acid, such as acetalwith tert-butoxy, combinations of a crosslinking acid labile group withacetal, and combinations of a crosslinking acid labile group with agroup differing in ease of cleavage under the action of acid, such astert-butoxy.

[0152] The proportion of the resin (B) which changes its solubility inan alkali developer under the action of acid and has substituents offormula (1) to the resin (C) which changes its solubility in an alkalideveloper under the action of acid and is free of substituents offormula (1) is not critical. When the resin (C) is added, it isrecommended that the content of the resin (C) is 0 to 99% by weight,especially 1 to 50% by weight based on the resins (B) and (C) combined.

[0153] Basic Compound (D)

[0154] The basic compound (D) is preferably a compound capable ofsuppressing the rate of diffusion when the acid generated by thephotoacid generator diffuses within the resist film. The inclusion ofthis type of basic compound holds down the rate of acid diffusion withinthe resist film, resulting in better resolution. In addition, itsuppresses changes in sensitivity following exposure and reducessubstrate and environment dependence, as well as improving the exposurelatitude and the pattern profile.

[0155] Examples of basic compounds include primary, secondary, andtertiary aliphatic amines, mixed amines, aromatic amines, heterocyclicamines, carboxyl group-bearing nitrogenous compounds, sulfonylgroup-bearing nitrogenous compounds, hydroxyl group-bearing nitrogenouscompounds, hydroxyphenyl group-bearing nitrogenous compounds, alcoholicnitrogenous compounds, amide derivatives, and imide derivatives.

[0156] Examples of suitable primary aliphatic amines include ammonia,methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine,isobutylamine, sec-butylamine, tert-butylamine, pentylamine,tert-amylamine, cyclopentylamine, hexylamine, cyclohexylamine,heptylamine, octylamine, nonylamine, decylamine, dodecylamine,cetylamine, methylenediamine, ethylenediamine, andtetraethylenepentamine. Examples of suitable secondary aliphatic aminesinclude dimethylamine, diethylamine, di-n-propylamine, diisopropylamine,di-n-butylamine, diisobutylamine, di-sec-butylamine, dipentylamine,dicyclopentylamine, dihexylamine, dicyclohexylamine, diheptylamine,dioctylamine, dinonylamine, didecylamine, didodecylamine, dicetylamine,N,N-dimethylmethylenediamine, N,N-dimethylethylenediamine, andN,N-dimethyltetraethylene-pentamine. Examples of suitable tertiaryaliphatic amines include trimethylamine, triethylamine,tri-n-propylamine, triisopropylamine, tri-n-butylamine,triisobutylamine, tri-sec-butylamine, tripentylamine,tricyclopentylamine, trihexylamine, tricyclohexylamine, triheptylamine,trioctylamine, trinonylamine, tridecylamine, tridodecylamine,tricetylamine, N,N,N′,N′-tetramethylmethylenediamine,N,N,N′,N′-tetramethylethylenediamine, andN,N,N′,N′-tetramethyltetraethylenepentamine.

[0157] Examples of suitable mixed amines include dimethylethylamine,methylethylpropylamine, benzylamine, phenethylamine, andbenzyldimethylamine. Examples of suitable aromatic and heterocyclicamines include aniline derivatives (e.g., aniline, N-methylaniline,N-ethylaniline, N-propylaniline, N,N-dimethylaniline, 2-methylaniline,3-methylaniline, 4-methylaniline, ethylaniline, propylaniline,trimethylaniline, 2-nitroaniline, 3-nitroaniline, 4-nitroaniline,2,4-dinitroaniline, 2,6-dinitroaniline, 3,5-dinitroaniline, andN,N-dimethyltoluidine), diphenyl(p-tolyl)amine, methyldiphenylamine,triphenylamine, phenylenediamine, naphthylamine, diaminonaphthalene,pyrrole derivatives (e.g., pyrrole, 2H-pyrrole, 1-methylpyrrole,2,4-dimethylpyrrole, 2,5-dimethylpyrrole, and N-methylpyrrole), oxazolederivatives (e.g., oxazole and isooxazole), thiazole derivatives (e.g.,thiazole and isothiazole), imidazole derivatives (e.g., imidazole,4-methylimidazole, and 4-methyl-2-phenylimidazole), pyrazolederivatives, furazan derivatives, pyrroline derivatives (e.g., pyrrolineand 2-methyl-1-pyrroline), pyrrolidine derivatives (e.g., pyrrolidine,N-methylpyrrolidine, pyrrolidinone, and N-methylpyrrolidone),imidazoline derivatives, imidazolidine derivatives, pyridine derivatives(e.g., pyridine, methylpyridine, ethylpyridine, propylpyridine,butylpyridine, 4-(1-butylpentyl)pyridine, dimethylpyridine,trimethylpyridine, triethylpyridine, phenylpyridine,3-methyl-2-phenylpyridine, 4-tert-butylpyridine, diphenylpyridine,benzylpyridine, methoxypyridine, butoxypyridine, dimethoxypyridine,1-methyl-2-pyridine, 4-pyrrolidinopyridine, 1-methyl-4-phenylpyridine,2-(1-ethylpropyl)pyridine, aminopyridine, and dimethylaminopyridine),pyridazine derivatives, pyrimidine derivatives, pyrazine derivatives,pyrazoline derivatives, pyrazolidine derivatives, piperidinederivatives, piperazine derivatives, morpholine derivatives, indolederivatives, isoindole derivatives, 1H-indazole derivatives, indolinederivatives, quinoline derivatives (e.g., quinoline and3-quinolinecarbonitrile), isoquinoline derivatives, cinnolinederivatives, quinazoline derivatives, quinoxaline derivatives,phthalazine derivatives, purine derivatives, pteridine derivatives,carbazole derivatives, phenanthridine derivatives, acridine derivatives,phenazine derivatives, 1,10-phenanthroline derivatives, adeninederivatives, adenosine derivatives, guanine derivatives, guanosinederivatives, uracil derivatives, and uridine derivatives.

[0158] Examples of suitable carboxyl group-bearing nitrogenous compoundsinclude aminobenzoic acid, indolecarboxylic acid, and amino acidderivatives (e.g. nicotinic acid, alanine, alginine, aspartic acid,glutamic acid, glycine, histidine, isoleucine, glycylleucine, leucine,methionine, phenylalanine, threonine, lysine,3-aminopyrazine-2-carboxylic acid, and methoxyalanine). Examples ofsuitable sulfonyl group-bearing nitrogenous compounds include3-pyridinesulfonic acid and pyridinium p-toluenesulfonate. Examples ofsuitable hydroxyl group-bearing nitrogenous compounds, hydroxyphenylgroup-bearing nitrogenous compounds, and alcoholic nitrogenous compoundsinclude 2-hydroxypyridine, aminocresol, 2,4-quinolinediol,3-indolemethanol hydrate, monoethanolamine, diethanolamine,triethanolamine, N-ethyldiethanolamine, N,N-diethyl-ethanolamine,truisopropanolamine, 2,2′-iminodiethanol, 2-aminoethanol,3-amino-1-propanol, 4-amino-1-butanol, 4-(2-hydroxyethyl)morpholine,2-(2-hydroxyethyl)pyridine, 1-(2-hydroxyethyl)piperazine,1-[2-(2-hydroxyethoxy)ethyl]-piperazine, piperidine ethanol,1-(2-hydroxyethyl)-pyrrolidine, 1-(2-hydroxyethyl)-2-pyrrolidinone,3-piperidino-1,2-propanediol, 3-pyrrolidino-1,2-propanediol,8-hydroxyjulolidine, 3-quinuclidinol, 3-tropanol, 1-methyl-2-pyrrolidineethanol, 1-aziridine ethanol, N-(2-hydroxyethyl)phthalimide, andN-(2-hydroxyethyl)-isonicotinamide. Examples of suitable amidederivatives include formamide, N-methylformamide, N,N-dimethylformamide,acetamide, N-methylacetamide, N,N-dimethylacetamide, propionamide, andbenzamide. Suitable imide derivatives include phthalimide, succinimide,and maleimide.

[0159] Also useful are substituted ones of the hydroxyl group-bearingnitrogenous compounds in which some or all of the hydrogen atoms onhydroxyl groups are replaced by methyl, ethyl, methoxymethyl,methoxyethoxymethyl, acetyl, or ethoxyethyl groups. Preferred aremethyl-, acetyl-, methoxymethyl- and methoxyethoxymethyl-substitutedcompounds of ethanolamine, diethanolamine and triethanolamine. Examplesinclude tris(2-methoxyethyl)amine, tris(2-ethoxyethyl)amine,tris(2-acetoxyethyl)amine, tris{2-(methoxymethoxy)ethyl}amine,tris{2-(methoxyethoxy)-ethyl}amine,tris[2-{(2-methoxyethoxy)methoxy}ethyl]amine,tris{2-(2-methoxyethoxy)ethyl}amine,tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine,tris{2-(1-ethoxypropoxy)-ethyl}amine, andtris[2-{(2-hydroxyethoxy)ethoxy}ethyl]amine.

[0160] The basic compounds may be used alone or in admixture of two ormore. The basic compound is preferably formulated in an amount of 0 to 2parts, and especially 0.01 to 1 part by weight, per 100 parts by weightof the base resin in the resist composition. The use of more than 2parts of the basis compound would result in too low a sensitivity.

[0161] Organic Acid Derivative (E)

[0162] Illustrative, non-limiting, examples of the organic acidderivatives (E) include phenol, cresol, catechol, resorcinol,pyrogallol, phloroglucinol, bis(4-hydroxyphenyl)methane,2,2-bis(4′-hydroxyphenyl)propane, bis(4-hydroxyphenyl)sulfone,1,1,1-tris(4′-hydroxyphenyl)ethane, 1,1,2-tris(4′-hydroxyphenyl)ethane,hydroxybenzophenone, 4-hydroxyphenylacetic acid, 3-hydroxyphenylaceticacid, 2-hydroxyphenylacetic acid, 3-(4-hydroxyphenyl)propionic acid,3-(2-hydroxyphenyl)propionic acid, 2,5-dihydroxyphenylacetic acid,3,4-dihydroxyphenylacetic acid, 1,2-phenylenediacetic acid,1,3-phenylenediacetic acid, 1,4-phenylenediacetic acid,1,2-phenylenedioxydiacetic acid, 1,4-phenylenedipropanoic acid, benzoicacid, salicylic acid, 4,4-bis(4′-hydroxyphenyl)valeric acid,4-tert-butoxyphenylacetic acid, 4-(4-hydroxyphenyl)butyric acid,3,4-dihydroxymandelic acid, and 4-hydroxymandelic acid. Of these,salicylic acid and 4,4-bis(41-hydroxyphenyl)valeric acid are preferred.They may be used alone or in admixture of two or more.

[0163] In the resist composition, the organic acid derivative ispreferably formulated in an amount of up to 5 parts, and especially upto 1 part by weight, per 100 parts by weight of the base resin in theresist composition. The use of more than 5 parts of the organic acidderivative would result in too low a resolution. Depending on thecombination of the other components in the resist composition, theorganic acid derivative may be omitted.

[0164] Component (F)

[0165] In one preferred embodiment, the resist composition furthercontains (F) a compound with a molecular weight of up to 3,000 whichchanges its solubility in an alkaline developer under the action of anacid, that is, a dissolution inhibitor. Typically, a compound obtainedby partially or entirely substituting acid labile substituents on aphenol or carboxylic acid derivative having a molecular weight of up to2,500 is added as the dissolution inhibitor.

[0166] Examples of the phenol or carboxylic acid derivative having amolecular weight of up to 2,500 include bisphenol A, bisphenol H,bisphenol S, 4,4-bis(4′-hydroxyphenyl)valeric acid,tris(4-hydroxyphenyl)methane, 1,1,1-tris(4′-hydroxyphenyl)ethane,1,1,2-tris(4′-hydroxyphenyl)ethane, phenolphthalein, andthimolphthalein. The acid labile substituents are the same as thoseexemplified as the acid labile groups in the polymer.

[0167] Illustrative, non-limiting, examples of the dissolutioninhibitors which are useful herein include

[0168] bis(4-(2′-tetrahydropyranyloxy)phenyl)methane,

[0169] bis(4-(2′-tetrahydrofuranyloxy)phenyl)methane,

[0170] bis(4-tert-butoxyphenyl)methane,

[0171] bis (4-tert-butoxycarbonyloxyphenyl)methane,

[0172] bis(4-tert-butoxycarbonylmethyloxyphenyl)methane,

[0173] bis(4-(1′-ethoxyethoxy)phenyl)methane,

[0174] bis(4-(1′-ethoxypropyloxy)phenyl)methane,

[0175] 2,2-bis(4′-(2″-tetrahydropyranyloxy))propane,

[0176] 2,2-bis(4′-(2″-tetrahydrofuranyloxy)phenyl)propane,

[0177] 2,2-bis(4′-tert-butoxyphenyl)propane,

[0178] 2,2-bis(4′-tert-butoxycarbonyloxyphenyl)propane,

[0179] 2,2-bis(4′-tert-butoxycarbonylmethyloxyphenyl)propane,

[0180] 2,2-bis(4′-(1″-ethoxyethoxy)phenyl)propane,

[0181] 2,2-bis(4′-(1″-ethoxypropyloxy)phenyl)propane,

[0182] tert-butyl 4,4-bis(4′-(2″-tetrahydropyranyloxy)phenyl)-valerate,

[0183] tert-butyl 4,4-bis(4′-(2″-tetrahydrofuranyloxy)phenyl)-valerate,

[0184] tert-butyl 4,4-bis(4′-tert-butoxyphenyl)valerate,

[0185] tert-butyl 4,4-bis(4-tert-butoxycarbonyloxyphenyl)valerate,

[0186] tert-butyl4,4-bis(4′-tert-butoxycarbonylmethyloxyphenyl)-valerate,

[0187] tert-butyl 4,4-bis(4′-(1″-ethoxyethoxy)phenyl)valerate,

[0188] tert-butyl 4,4-bis(4′-(1″-ethoxypropyloxy)phenyl)valerate,

[0189] tris(4-(2′-tetrahydropyranyloxy)phenyl)methane,

[0190] tris(4-(2′-tetrahydrofuranyloxy)phenyl)methane,

[0191] tris(4-tert-butoxyphenyl)methane,

[0192] tris(4-tert-butoxycarbonyloxyphenyl)methane,

[0193] tris(4-tert-butoxycarbonyloxymethylphenyl)methane,

[0194] tris(4-(1′-ethoxyethoxy)phenyl)methane,

[0195] tris(4-(1′-ethoxypropyloxy)phenyl)methane,

[0196] 1,1,2-tris(4′-(2″-tetrahydropyranyloxy)phenyl)ethane,

[0197] 1,1,2-tris(4′-(2″-tetrahydrofuranyloxy)phenyl)ethane,

[0198] 1,1,2-tris(4′-tert-butoxyphenyl)ethane,

[0199] 1,1,2-tris(4′-tert-butoxycarbonyloxyphenyl)ethane,

[0200] 1,1,2-tris(4′-tert-butoxycarbonylmethyloxyphenyl)ethane,

[0201] 1,1,2-tris(4′-(1′-ethoxyethoxy)phenyl)ethane, and

[0202] 1,1,2-tris(4′-(1′-ethoxypropyloxy)phenyl)ethane.

[0203] In the resist composition, an appropriate amount of thedissolution inhibitor is up to 20 parts, and especially up to 15 partsby weight per 100 parts by weight of the base resin in the composition.With more than 20 parts of the dissolution inhibitor, the resistcomposition becomes less heat resistant because of an increased contentof monomer components.

[0204] In the chemically amplified positive resist composition of theinvention, there may be added an acid-propagating compound, a surfactantfor improving coating characteristics, and a light absorber for reducingdiffuse reflection from the substrate.

[0205] The acid-propagating compound is a compound which is decomposedwith an acid to generate an acid. For these compounds, reference shouldbe made to J. Photopolym. Sci. and Tech., 8, 43-44, 45-46 (1995), andibid., 9, 29-30 (1996).

[0206] Examples of the acid-propagating compound includetert-butyl-2-methyl-2-tosyloxymethyl acetoacetate and2-phenyl-2-(tosyloxyethyl)-1,3-dioxoran, but are not limited thereto. Ofwell-known photoacid generators, many of those compounds having poorstability, especially poor thermal stability exhibit an acid-propagatingcompound-like behavior.

[0207] In the resist composition, an appropriate amount of theacid-propagating compound is up to 2 parts, and especially up to 1 partby weight per 100 parts by weight of the base resin in the composition.Excessive amounts of the acid-propagating compound makes diffusioncontrol difficult, leading to degradation of resolution and patternconfiguration.

[0208] Illustrative, non-limiting, examples of the surfactant includenonionic surfactants, for example, polyoxyethylene alkyl ethers such aspolyoxyethylene lauryl ether, polyoxyethylene stearyl ether,polyoxyethylene cetyl ether, and polyoxyethylene oleyl ether,polyoxyethylene alkylaryl ethers such as polyoxyethylene octylphenolether and polyoxyethylene nonylphenol ether, polyoxyethylenepolyoxypropylene block copolymers, sorbitan fatty acid esters such assorbitan monolaurate, sorbitan monopalmitate, and sorbitan monostearate,and polyoxyethylene sorbitan fatty acid esters such as polyoxyethylenesorbitan monolaurate, polyoxyethylene sorbitan monopalmitate,polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitantrioleate, and polyoxyethylene sorbitan tristearate; fluorochemicalsurfactants such as EFTOP EF301, EF303 and EF352 (Tohkem Products K.K.),Megaface F171, F172 and F173 (Dai-Nippon Ink & Chemicals K.K.), FloradeFC430 and FC431 (Sumitomo 3M K.K.), Aashiguard AG710, Surflon S-381,S-382, SC101, SC102, SC103, SC104, SC105, SC106, Surfynol E1004, KH-10,KH-20, KH-30 and KH-40 (Asahi Glass K.K.); organosiloxane polymersKP341, X-70-092 and X-70-093 (Shin-Etsu Chemical Co., Ltd.), acrylicacid or methacrylic acid Polyflow No. 75 and No. 95 (Kyoeisha UshiKagaku Kogyo K.K.). Inter alia, FC430, Surflon S-381, Surfynol E1004,KH-20 and KH-30 are preferred. These surfactants may be used alone or inadmixture.

[0209] In the resist composition, the surfactant is preferablyformulated in an amount of up to 2 parts, and especially up to 1 part byweight, per 100 parts by weight of the base resin in the resistcomposition.

[0210] In the chemically amplified positive resist composition, a UVabsorber may be added.

[0211] Exemplary UV absorbers are fused polycyclic hydrocarbonderivatives such as pentalene, indene, naphthalene, azulene, heptalene,biphenylene, indacene, fluorene, phenalene, phenanthrene, anthracene,fluoranthene, acephenanthrylene, aceanthrylene, triphenylene, pyrene,chrysene, pleiadene, picene, perylene, pentaphene, pentacene,benzophenanthrene, anthraquinone, anthrone, benzanthrone,2,7-dimethoxynaphthalene, 2-ethyl-9,10-dimethoxyanthracene,9,10-dimethylanthracene, 9-ethoxyanthracene, 1,2-naphthoquinone,9-fluorene, and compounds of the following formulae (D1) and (D2); fusedheterocyclic derivatives such as thioxanthen-9-one, thianthrene,dibenzothiophene; benzophenone derivatives such as2,3,4-trihydroxy-benzophenone, 2,3,4,4′-tetrahydroxybenzophenone,2,4-dihydroxybenzophenone, 3,5-dihydroxybenzophenone,4,4′-dihydroxybenzophenone, and 4,4′-bis(dimethylamino)-benzophenone;squalic acid derivatives such as squalic acid and dimethyl squalate;diaryl sulfoxide derivatives such as bis(4-hydroxyphenyl) sulfoxide,bis(4-tert-butoxyphenyl) sulfoxide, bis(4-tert-butoxycarbonyloxyphenyl)sulfoxide, and bis[4-(1-ethoxyethoxy)phenyl] sulfoxide; diarylsulfonederivatives such as bis(4-hydroxyphenyl)sulfone,bis(4-tert-butoxyphenyl)sulfone,bis(4-tert-butoxycarbonyloxyphenyl)-sulfone,bis[4-(1-ethoxyethoxy)phenyl]sulfone, andbis[4-(1-ethoxypropoxy)phenyl]sulfone; diazo compounds such asbenzoquinonediazide, naphthoquinonediazide, anthraquinonediazide,diazofluorene, diazotetralone, and diazophenanthrone; quinonediazidegroup-containing compounds such as complete or partial ester compoundsbetween naphthoquinone-1,2-diazide-5-sulfonic acid chloride and2,3,4-trihydroxybenzophenone and complete or partial ester compoundsbetween naphthoquinone-1,2-diazide-4-sulfonic acid chloride and2,4,4′-trihydroxybenzophenone; tert-butyl 9-anthracenecarboxylate,tert-amyl 9-anthracenecarboxylate, tert-methoxymethyl9-anthracenecarboxylate, tert-ethoxyethyl 9-anthracenecarboxylate,2-tert-tetrahydropyranyl 9-anthracenecarboxylate, and2-tert-tetrahydrofuranyl 9-anthracenecarboxylate.

[0212] Herein, R⁶¹ to R⁶³ are independently hydrogen or a straight orbranched alkyl, straight or branched alkoxy, straight or branchedalkoxyalkyl, straight or branched alkenyl or aryl group. R⁶⁴ is asubstituted or unsubstituted divalent aliphatic hydrocarbon group whichmay contain an oxygen atom, a substituted or unsubstituted divalentalicyclic hydrocarbon group which may contain an oxygen atom, asubstituted or unsubstituted divalent aromatic hydrocarbon group whichmay contain an oxygen atom, or an oxygen atom. R⁶⁵ is an acid labilegroup as described above. Letter J is equal to 0 or 1, EE, F and G are 0or integers of 1 to 9, H is a positive integer of 1 to 10, satisfyingEE+F+G+H≦10.

[0213] An appropriate amount of UV absorber blended is 0 to 10 parts,more preferably 0.5 to 10 parts, most preferably 1 to 5 parts by weightper 100 parts by weight of the base resin in the resist composition.

[0214] For the microfabrication of integrated circuits, any well-knownlithography may be used to form a resist pattern from the chemicalamplification, positive working, resist composition comprising (A) thephotoacid generator and (B) the resin which changes its solubility in analkali developer under the action of acid and has substituents offormula (1) according to the invention.

[0215] The composition is applied onto a substrate (e.g., Si, SiO₂, SiN,SiON, TiN, WSi, BPSG, SOG, organic anti-reflecting film, etc.) by asuitable coating technique such as spin coating, roll coating, flowcoating, dip coating, spray coating or doctor coating. The coating isprebaked on a hot plate at a temperature of 60 to 150° C. for about 1 to10 minutes, preferably 80 to 120° C. for 1 to 5 minutes. The resultingresist film is generally 0.1 to 2.0 μm thick. With a mask having adesired pattern placed above the resist film, the resist film is thenexposed to actinic radiation, preferably having an exposure wavelengthof up to 300 nm, such as UV, deep-UV, electron beams, x-rays, excimerlaser light, γ-rays and synchrotron radiation in an exposure dose ofabout 1 to 200 mJ/cm², preferably about 10 to 100 mJ/cm². The film isfurther baked on a hot plate at 60 to 150° C. for 1 to 5 minutes,preferably 80 to 120° C. for 1 to 3 minutes (post-exposure baking=PEB).

[0216] Thereafter the resist film is developed with a developer in theform of an aqueous base solution, for example, 0.1 to 5%, preferably 2to 3% aqueous solution of tetramethylammonium hydroxide (TMAH) for 0.1to 3 minutes, preferably 0.5 to 2 minutes by conventional techniquessuch as dipping, puddling or spraying. In this way, a desired resistpattern is formed on the substrate. It is appreciated that the resistcomposition of the invention is best suited for micro-patterning usingsuch actinic radiation as deep UV with a wavelength of 254 to 193 nm,vacuum UV with a wavelength of 157 nm, electron beams, x-rays, excimerlaser light, γ-rays and synchrotron radiation. With any of theabove-described parameters outside the above-described range, theprocess may sometimes fail to produce the desired pattern.

EXAMPLE

[0217] Examples of the invention are given below by way of illustrationand not by way of limitation.

Synthesis Example 1

[0218] Synthesis of Allyl Benzyl Ether

[0219] In 870 g of tetrahydrofuran were dissolved 218 g (2 mol) ofbenzyl alcohol and 224 g (2 mol) of potassium t-butoxide. With stirringat room temperature, 242 g (2 mol) of allyl bromide was added dropwiseso that the temperature might not exceed 60° C. At the end of addition,the solution was heated at 60° C. on an oil bath and ripened for onehour at the temperature. The solution was allowed to cool down to roomtemperature, and 11.2 g (0.1 mol) of potassium t-butoxide was added.With stirring at room temperature, 12.1 g (0.1 mol) of allyl bromide wasadded dropwise. The solution was heated at 60° C. on an oil bath andripened for one hour at the temperature. The solution was cooled in anice bath, and 550 g of water was added. The organic layer was collected.The solvent was distilled off in vacuum, yielding 299 g of a crude endproduct. The product was used -in the subsequent reaction withoutfurther purification.

Synthesis Example 2

[0220] Synthesis of Benzyl Propenyl Ether

[0221] A mixture of 299 g of the crude product, 300 g of dimethylsulfoxide, and 22.5 g (0.2 mol) of potassium t-butoxide was heated at100° C. on the oil bath and ripened for 2 hours at the temperature. Thesolution was allowed to cool, and 650 g of water and 600 g of n-hexanewere added thereto, from which the organic layer was collected. Theorganic layer was washed with 250 g of water, and the solvent wasdistilled off in vacuum, leaving 300 g of an oily substance. The oilysubstance was subjected to vacuum distillation, obtaining 258 g of theend product, benzyl propenyl ether. The yield was 87% (two steps) andthe purity was 99.4% as analyzed by gas chromatography.

[0222] The results of nuclear magnetic resonance spectroscopy, infraredabsorption spectroscopy and elemental analysis of the compound are shownbelow. ¹H-NMR: CDCl₃ (ppm)

Ha: 1.64-1.67 multiplet 3H Hb: 4.45-4.51 multiplet 1H Hc: 6.03-6.05multiplet 1H Hd: 4.82 singlet 2H Hf: 7.30-7.42 multiplet 5H

[0223] 3089, 3064, 3034, 2971, 2919, 2868, 1809, 1728, 1668, 1587, 1497,1454, 1404, 1375, 1356, 1290, 1272, 1255, 1207, 1124, 1093, 1074, 1028,985, 957, 908, 732

[0224] Elemental analysis for C₁₀H₁₂O₁ (%)

[0225] Calcd.C 81.0H 8.2

[0226] Found C 81.5H 8.1

Synthesis Example 3

[0227] Synthesis ofpoly(p-(1-benzyloxypropyl)oxystyrene/p-hydroxystyrene)

[0228] In 48 g of tetrahydrofuran was dissolved 12 g ofpoly(p-hydroxystyrene) having a weight average molecular weight (Mw) of9,000 and a dispersity (Mw/Mn) of 1.05. A catalytic amount ofp-toluenesulfonic acid was added. At 10° C., 4.3 g (0.029 mol) of benzylpropenyl ether was added to the solution, which was stirred for 2 hours.The reaction mixture was precipitated from a water/isopropanol mixture,followed by filtration and drying. The end polymer was obtained in anamount of 13.5 g. On ¹H-NMR analysis, the ratio ofp-(1-benzyloxypropyl)oxystyrene units to p-hydroxystyrene units wasapproximately 22.5:77.5.

[0229] The polymer had a weight average molecular weight (Mw) of about11,000 as analyzed by GPC and calculated on a polystyrene basis and adispersity (Mw/Mn) of 1.10.

Synthesis Example 4

[0230] Synthesis of Tri-Branched poly(p-hydroxystyrene)

[0231] A 1-liter flask was charged with 500 ml of tetrahydrofuran as asolvent and 0.01 mol of sec-butyl lithium as an initiator. To thesolution at −78° C. was added 40 g of p-tert-butoxystyrene. Withstirring, polymerization reaction was effected for 30 minutes. Thereaction solution turned red. For producing a branched polymer, 0.005mol of p-chloromethylstyrene was added to the reaction solutionwhereupon reaction was effected for 5 minutes. The reaction solution wasred. Further 20 g of p-tert-butoxystyrene was added. With stirring,polymerization reaction was effected for 30 minutes. Polymerization wasstopped by adding 0.1 mol of methanol to the reaction solution.

[0232] For purifying the polymer, the reaction mixture was poured intomethanol whereupon the polymer precipitated. Separation and dryingyielded 44 g of a white polymer which was tri-branchedpoly(p-tert-butoxystyrene).

[0233] For producing tri-branched poly(p-hydroxystyrene), 44 g of theabove tri-branched poly(p-tert-butoxystyrene) was dissolved in 400 ml ofacetone. A minor amount of conc. hydrochloric acid was added to thesolution at 60° C., which was stirred for 7 hours. The reaction solutionwas poured into water whereupon the polymer precipitated. Washing anddrying yielded 25 g of a white polymer. Since a peak attributable totert-butyl group was not found in GPC and proton-NMR analysis, thispolymer was confirmed to be tri-branched poly(p-hydroxystyrene) having anarrow molecular weight distribution.

[0234] The polymer had a weight average molecular weight (Mw) of 8,500as analyzed by GPC and calculated on a polystyrene basis and adispersity (Mw/Mn) of 1.10.

Synthesis Example 5

[0235] Synthesis of Tri-Branchedpoly(p-(1-benzyloxypropyl)-oxystyrene/p-hydroxystyrene)

[0236] On the tri-branched poly(p-hydroxystyrene) synthesized inSynthesis Example 4, 1-benzyloxypropyl groups were partially substitutedas in Synthesis Example 3.

Synthesis Example 6

[0237] Synthesis of Nona-Branched poly(p-hydroxystyrene)

[0238] A 2-liter flask was charged with 1000 ml of tetrahydrofuran as asolvent and 0.06 mol of sec-butyl lithium as an initiator. To thesolution at −78° C. was added 60 g of p-tert-butoxystyrene. Withstirring, polymerization reaction was effected for 30 minutes. Thereaction solution turned red. For producing a tri-branched polymer, 0.03mol of p-chloromethylstyrene was added to the reaction solutionwhereupon reaction was effected for 5 minutes. Then 30 g ofp-tert-butoxystyrene was added to the reaction solution, which wasstirred for 30 minutes for polymerization. The reaction solution wasred. For producing penta-branched polymer, 0.015 mol ofp-chloromethylstyrene was added to the reaction solution whereuponreaction was effected for 5 minutes. Then 15 g of p-tert-butoxystyrenewas added to the reaction solution, which was stirred for 30 minutes forpolymerization. The reaction solution was red. Finally for producingnona-branched polymer, 0.0075 mol of p-chloromethylstyrene was added tothe reaction solution whereupon reaction was effected for 5 minutes.Then 7.5 g of p-tert-butoxystyrene was added to the reaction solution,which was stirred for 30 minutes for polymerization. The reactionsolution was red. Polymerization was stopped by adding 0.1 mol of carbondioxide gas to the reaction solution.

[0239] For purifying the polymer, the reaction mixture was poured intomethanol whereupon the polymer precipitated. Separation and dryingyielded 99 g of a white polymer which was nona-branchedpoly(p-tert-butoxystyrene).

[0240] For converting to nona-branched poly(p-hydroxy-styrene), 99 g ofthe above nona-branched poly(p-tert-butoxystyrene) was dissolved in 1000ml of acetone. A minor amount of conc. hydrochloric acid was added tothe solution at 60° C., which was stirred for 7 hours. The reactionsolution was poured into water whereupon the polymer precipitated.Washing and drying yielded 66 g of a white polymer. Since a peakattributable to tert-butyl group was not found on GPC and proton-NMRanalysis, this polymer was confirmed to be nona-branchedpoly(p-hydroxystyrene) having a narrow molecular weight distribution.

[0241] The polymer had a weight average molecular weight (Mw) of 11,000as analyzed by GPC and calculated on a polystyrene basis and adispersity (Mw/Mn) of 1.25.

Synthesis Example 7

[0242] Synthesis of Nona-Branchedpoly(p-(1-benzyloxypropyl)-oxystyrene/p-hydroxystyrene)

[0243] On the nona-branched poly(p-hydroxystyrene) synthesized inSynthesis Example 6, 1-benzyloxypropyl groups were partially substitutedas in Synthesis Example 3.

Examples & Comparative Examples

[0244] Resist compositions were prepared according to the formulationshown in Tables 1 to 3. The components listed in Tables 1 to 3 have thefollowing meaning.

[0245] Polymer A: poly(p-hydroxystyrene) in which hydroxyl groups areprotected with 23 mol % of 1-benzyloxypropyl groups, having a weightaverage molecular weight of 11,000.

[0246] Polymer B: poly(p-hydroxystyrene) in which hydroxyl groups areprotected with 10 mol % of 1-benzyloxypropyl groups and 10 mol % oftert-butoxycarbonyl groups, having a weight average molecular weight of11,000.

[0247] Polymer C: nano-branched poly(p-hydroxystyrene) in which hydroxylgroups are protected with 15 mol % of 1-benzyloxypropyl groups and 5 mol% of tert-butoxycarbonyl groups, having a weight average molecularweight of 14,000.

[0248] Polymer D: poly(p-hydroxystyrene) in which hydroxyl groups areprotected with 20 mol % of 1-benzyloxypropyl groups and crosslinked with1 mol % of 1,2-propane diol divinyl ether, having a weight averagemolecular weight of 13,000.

[0249] Polymer E: tri-branched poly(p-hydroxystyrene) in which hydroxylgroups are protected with 20 mol % of 1-benzyloxypropyl groups, having aweight average molecular weight of 11,000.

[0250] Polymer F: poly(p-hydroxystyrene) in which hydroxyl groups areprotected with 22 mol % of 1-phenethyloxypropyl groups, having a weightaverage molecular weight of 12,000.

[0251] Polymer G: poly(p-hydroxystyrene) in which hydroxyl groups areprotected with 20 mol % of 1-phenethyloxypropyl groups and crosslinkedwith 1 mol % of 1,4-butane diol divinyl ether, having a weight averagemolecular weight of 13,000.

[0252] Polymer H: p-hydroxystyrene/1-ethylcyclopentyl methacrylatecopolymer having a compositional ratio (molar ratio) of 90:10, hydroxylgroups in the p-hydroxystyrene being protected with 15 mol % of1-benzyloxypropyl groups, the copolymer having a weight averagemolecular weight of 12,000.

[0253] Polymer I: p-hydroxystyrene/tert-butyl acrylate copolymer havinga compositional ratio (molar ratio) of 80:20, hydroxyl groups in thep-hydroxystyrene being protected with 10 mol % of 1-benzyloxypropylgroups, the copolymer having a weight average molecular weight of12,000.

[0254] Polymer J: the same as Polymer I further containing 5% by weightof styrene and having a weight average molecular weight of 12,000.

[0255] Polymer K: p-hydroxystyrene/1-ethylcyclopentyl methacrylatecopolymer having a compositional ratio (molar ratio) of 90:10, hydroxylgroups in the p-hydroxystyrene being protected with 10 mol % of1-benzyloxypropyl groups and crosslinked with 2 mol % of 1,4-butane dioldivinyl ether, the copolymer having a weight average molecular weight of13,000.

[0256] Polymer L: poly(p-hydroxystyrene) in which hydroxyl groups areprotected with 25 mol % of 1-ethoxypropyl groups and crosslinked with 3mol % of 1,2-propane diol divinyl ether, having a weight averagemolecular weight of 13,000.

[0257] Polymer M: poly(p-hydroxystyrene) in which hydroxyl groups areprotected with 15 mol % of 1-ethoxyethyl groups and 15 mol % oftert-butoxycarbonyl groups, having a weight average molecular weight of12,000.

[0258] Polymer N: p-hydroxystyrene/1-ethylcyclopentyl methacrylatecopolymer having a compositional ratio (molar ratio) of 70:30 and aweight average molecular weight of 11,000.

[0259] PAG1: triphenylsulfonium 4-toluenesulfonate

[0260] PAG2: (4-butoxyphenyl)diphenylsulfonium 10-camphorsulfonate

[0261] PAG3: bis(4-butylphenyl)iodonium 10-camphorsulfonate

[0262] PAG4: triphenylsulfonium 4-(4-toluenesulfonyloxy)benzene-sulfonate

[0263] PAG5: tris(4-butoxyphenyl)sulfonium nonafluorobutane- sulfonate

[0264] PAG6: N-(10-camphorsulfonyl)oxy-1,9-naphthalenedicarboxylic acidimide

[0265] PAG7: bis(cyclohexylsulfonyl)diazomethane

[0266] PAG8: bis(tert-butylsulfonyl)diazomethane

[0267] PAG9: bis(2,4-dimethylphenylsulfonyl)diazomethane

[0268] Basic compound A: triethanolamine

[0269] Basic compound B: tris(2-ethoxyethyl)amine

[0270] Organic acid derivative A: 4,4-bis(4′-hydroxyphenyl)valeric acid

[0271] Organic acid derivative B: salicylic acid

[0272] Surfactant A: FC-430 (Sumitomo 3M K.K.)

[0273] Surfactant B: Surflon S-381 (Asahi Glass K.K.)

[0274] UV absorber: 9,10-dimethylanthracene

[0275] Solvent A: propylene glycol methyl ether acetate

[0276] Solvent B: ethyl lactate

[0277] Each resist solution was passed through a 0.2 μm Teflon filterand spin coated onto a silicon wafer which had been coated with anorganic antireflection film (DUV-44 by Brewer Science) to a thickness of800 Å. The coated silicon wafer was baked on a hot plate at 100° C. for90 seconds. The thickness of the resist film was set at 0.6 μm.

[0278] The resist film was exposed through the patterned mask using anexcimer laser stepper (NSR-S202A, from Nikon Corporation; NA=0.6 2/3annular) baked at 110° C. for 90 seconds (PEB) and developed with a 2.38wt % solution of tetramethylammonium hydroxide in water, thereby givinga positive pattern (Examples 1-24 and Comparative Examples 1-3).

[0279] The resist patterns obtained were evaluated as described below.

[0280] Resist Pattern Evaluation

[0281] The optimal exposure dose (sensitivity, Eop) was defined as thedose which provides a 1:1 resolution at the top and bottom of a 0.15 μmline-and-space pattern. The resolution of the resist under evaluationwas defined as the minimum line width of the lines and spaces thatseparated at this dose. The shape in cross section of the resolvedresist pattern was examined under a scanning electron microscope.

[0282] The depth of focus (DOF) was determined by offsetting the focalpoint and judging the resist to be passed when the resist pattern shapewas kept rectangular and the resist pattern film thickness was keptabove 80% of that at accurate focusing.

[0283] The PED stability of a resist was evaluated by effectingpost-exposure bake (PEB) after 24 hours of holding from exposure at theoptimum dose and determining a variation in line width.

[0284] The results of resist pattern evaluation are shown in Table 4.

[0285] Other Evaluation

[0286] The solubility of resist material in a solvent mixture wasexamined by visual observation and in terms of clogging upon filtration.

[0287] With respect to the applicability of a resist solution, unevencoating was visually observed. Additionally, using a film gage CleanTrack Mark 8 (Tokyo Electron K.K.), the thickness of a resist film on acommon wafer was measured at different positions, based on which avariation from the desired coating thickness (0.6 μm) was calculated.The applicability was rated “good” when the variation was within 0.5%(that is, within 0.003 μm), “unacceptable” when the variation was within1%, and “poor” when the variation was more than 1%.

[0288] Storage stability was judged in terms of particle precipitationor sensitivity change during aging. After the resist solution was agedfor 100 days at the longest, the number of particles of greater than 0.3μm per ml of the resist solution was counted by means of a particlecounter KL-20A (Rion K.K.), and the particle precipitation wasdetermined “good” when the number of particles is not more than 5. Also,the sensitivity change was rated “good” when a change with time ofsensitivity (Eop) was within 5% from that immediately after preparation,and “poor” when the change is more than 5%.

[0289] Defect appearing on the developed pattern was observed under ascanning electron microscope (TDSEM) model S-7280H (Hitachi K.K.). Theresist film was rated “good” when the number of foreign particles was upto 10 per 100 μm², “unacceptable” when from 11 to 15, and “poor” whenmore than 15.

[0290] Defect left after resist stripping was examined using a surfacescanner Surf-Scan 6220 (Tencol Instruments). A resist-coated 8-inchwafer was subjected to entire exposure rather than patterned exposure,processed in a conventional manner, and developed with a 2.38% TMAHsolution before the resist film was peeled off (only the resist film inthe exposed area was peeled). After the resist film was peeled, thewafer was examined and rated “good” when the number of foreign particlesof greater than 0.20 μm was up to 100, “unacceptable” when from 101 to150, and “poor” when more than 150.

[0291] The results are shown in Table 5. TABLE 1 Composition (pbw) E1 E2E3 E4 E5 E6 E7 E8 E9 E10 E11 E12 Polymer A 80 40 Polymer B 80 Polymer C80 Polymer D 80 Polymer E 80 Polymer F 80 Polymer G 80 Polymer H 80 40Polymer I 80 Polymer J 40 Polymer K 80 Polymer L 40 Polymer M Polymer NPAG1 2 PAG2 2 2 2 2 2 PAG3 2 1 2 2 PAG4 2 2 2 PAG5 1 1 PAG6 2 2 PAG7 2 2PAG8 1 PAG9 1.5 1 1 1 Dissolution inhibitor Basic compound A 0.3 0.3 0.30.3 0.3 0.15 0.3 0.3 Basic compound B 0.3 0.15 0.3 0.3 0.3 Organic acid1 1 1 1 1 1 1 derivative A Organic acid 1 1 1 1 1 derivative BSurfactant A 0.25 0.25 0.25 0.25 0.25 0.25 Surfactant B 0.25 0.25 0.250.25 0.25 0.25 UV absorber Solvent A 385 280 385 280 280 280 280 280 280280 280 280 Solvent B 105 105 105 105 105 105 105 105 105 105

[0292] TABLE 2 Composition (pbw) E13 E14 E15 E16 E17 E18 E19 E20 E21 E22E23 E24 Polymer A 40 40 60 Polymer B 20 75 Polymer C 20 40 80 Polymer D40 40 60 40 Polymer E 40 Polymer F Polymer G 40 40 Polymer H 60 40Polymer I 20 Polymer J Polymer K 40 60 Polymer L 20 Polymer M 20 PolymerN PAG1 2 20 PAG2 2 2 2 PAG3 2 1 2 2 2 1 PAG4 2 2 2 PAG5 1 1 1 PAG6 2 2PAG7 2.5 1.5 PAG8 0.5 PAG9 1.5 1 1 1 Dissolution 5 inhibitor Basiccompound A 0.15 0.3 0.3 0.3 Basic compound B 0.15 0.3 0.3 0.3 0.3 0.30.3 0.3 0.3 Organic acid 1 1 1 1 1 1 derivative A Organic acid 1 1 1 1 11 1 derivative B Surfactant A 0.25 0.25 0.25 0.25 0.25 0.25 0.25Surfactant B 0.25 0.25 0.25 0.25 0.25 UV absorber 0.5 Solvent A 385 280280 280 385 280 280 280 280 280 280 280 Solvent B 105 105 105 105 105105 105 105 105 105

[0293] TABLE 3 Composition (pbw) CE1 CE2 CE3 Polymer L 80 Polymer M 80Polymer N 80 PAG1 PAG2 PAG3 PAG4 PAG5 PAG6 PAG7 PAG8 2 2 PAG9 2Dissolution inhibitor Basic compound A 0.3 Basic compound B 0.3 0.3Organic acid derivative A 1 1 1 Organic acid derivative B Surfactant A0.25 0.25 Surfactant B 0.25 UV absorber Solvent A 280 385 280 Solvent B105 105

[0294] TABLE 4 DOF for 24 hr PED Sensitivity Resolution Profile 0.15 μmProfile dimensional (mJ/cm²) (μm) shape (μm) shape* stability (nm) E1 26 0.14 rectangular 1.0 rectangular −10 E2  30 0.14 rectangular 1.0rectangular −5 E3  27 0.14 rectangular 1.0 rectangular −8 E4  25 0.14rectangular 0.9 rectangular −8 E5  27 0.14 rectangular 1.0 rectangular−10 E6  30 0.15 rectangular 1.0 rectangular −6 E7  28 0.14 rectangular1.0 rectangular −8 E8  27 0.14 rectangular 1.0 rectangular −12 E9  320.14 rectangular 1.0 rectangular −10 E10 30 0.14 rectangular 1.0rectangular −10 E11 28 0.14 rectangular 1.0 rectangular −8 E12 27 0.14rectangular 1.0 rectangular −10 E13 27 0.14 rectangular 1.0 rectangular−8 E14 26 0.14 rectangular 1.0 rectangular −10 E15 26 0.14 rectangular1.0 rectangular −10 E16 26 0.15 rectangular 1.0 rectangular −8 E17 280.14 rectangular 1.0 rectangular −10 E18 27 0.14 rectangular 1.0rectangular −8 E19 27 0.14 rectangular 1.0 rectangular −10 E20 28 0.14rectangular 1.0 rectangular −10 E21 26 0.14 rectangular 1.0 rectangular−10 E22 28 0.14 rectangular 1.0 rectangular −10 E23 27 0.14 rectangular1.0 rectangular −8 E24 26 0.14 rectangular 1.0 rectangular −8 somewhatCE1 23 0.15 rounded head 0.6 rounded head −10 CE2 27 0.15 rounded head0.6 rounded head −8 CE3 27 0.15 forward 0.6 forward −10 tapered tapered

[0295] TABLE 5 100 day storage Defect after Dissolution Applicationstability Development E1  good good good good E2  good good good goodE3  good good good good E4  good good good good E5  good good good goodE6  good good good good E7  good good good good E8  good good good goodE9  good good good good E10 good good good good E11 good good good goodE12 good good good good E13 good good good good E14 good good good goodE15 good good good good E16 good good good good E17 good good good goodE18 good good good good E19 good good good good E20 good good good goodE21 good good good good E22 good good good good E23 good good good goodE24 good good good good CE1 good good <30 days good (sensitivitychanged) CE2 good unacceptable <30 days unacceptable (sensitivitychanged) CE3 good good good poor

[0296] There have been described chemical amplification type positiveresist compositions comprising a resin having substituents of formula(1). The compositions have many advantages including improvedresolution, minimized line width variation or shape degradation even onlong-term PED, minimized defect left after coating, development andstripping, and improved pattern profile after development. Thecompositions are improved in focal latitude in that the pattern profilemaintains rectangularity and undergoes minimized slimming when the focalpoint is offset. The compositions are thus suited for microfabricationby any lithography, especially deep UV lithography.

[0297] Japanese Patent Application No. 2000-061350 is incorporatedherein by reference.

[0298] Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

1. A chemical amplification, positive resist composition comprising (A)a photoacid generator and (B) a resin which changes its solubility in analkali developer under the action of acid and has substituents of thefollowing general formula (1): Ph—(CH₂)_(n)OCH(CH₂CH₃)—  (1) wherein Phis phenyl and n is 1 or
 2. 2. The resist composition of claim 1 whereinthe resin (B) is an alkali-soluble resin comprising units of thefollowing formula (2) or (2′) wherein some or all of the hydrogen atomson phenolic hydroxyl groups and/or carboxyl groups are protected withsubstituents of the formula (1),

wherein R⁴ is hydrogen or methyl, R⁵ is a straight, branched or cyclicalkyl group of 1 to 8 carbon atoms, x is 0 or a positive integer, y is apositive integer, satisfying x+y≦5, M and N are positive integerssatisfying 0<N/(M+N)≦0.5.
 3. The resist composition of claim 1 whereinthe resin (B) is a branched, alkali-soluble resin comprising units ofthe following formula (2″) wherein some of the hydrogen atoms onphenolic hydroxyl groups are protected with substituents of the formula(1),

wherein R⁴, R⁵, x and y are as defined above, ZZ is a divalent organicgroup selected from the group consisting of CH₂, CH(OH), CR⁵(OH), C═O,and C(OR⁵)(OH), or a trivalent organic group represented by —C(OH)═, Emay be the same or different and is a positive integer, K is a positiveinteger, satisfying 0.001≦K/(K+E)≦0.1, and XX is 1 or
 2. 4. The resistcomposition of claim 1 wherein the resin (B) further has acid labilegroups.
 5. The resist composition of claim 1 wherein the resin (B)further has acid labile groups which are selected from the classconsisting of groups of the following general formulae (4) to (7),tertiary alkyl groups of 4 to 20 carbon atoms, trialkylsilyl groups inwhich each alkyl moiety has 1 to 6 carbon atoms, and oxoalkyl groups of4 to 20 carbon atoms,

wherein R¹⁰ and R¹¹ each are hydrogen or a straight, branched or cyclicalkyl group of 1 to 18 carbon atoms, R¹² is a monovalent hydrocarbongroup of 1 to 18 carbon atoms which may contain a hetero atom such asoxygen atom, a pair of R¹⁰ and R¹¹, R¹⁰ and R¹², or R¹¹ and R¹² may forma ring, each of R¹⁰, R¹¹ and R12 is a straight or branched alkylenegroup of 1 to 18 carbon atoms when they form a ring, R¹³ is a tertiaryalkyl group of 4 to 20 carbon atoms, a trialkylsilyl group in which eachalkyl moiety has 1 to 6 carbon atoms, an oxoalkyl group of 4 to 20carbon atoms, or a group of formula (4), z is an integer of 0 to 6, R¹⁴is a straight, branched or cyclic alkyl group of 1 15 to 8 carbon atomsor a substituted or unsubstituted aryl group of 6 to 20 carbon atoms, his equal to 0 or 1, and is equal to 0, 1, 2 or 3, satisfying 2h+i=2 or3, R¹⁵ is a straight, branched or cyclic alkyl group of 1 to 8 carbonatoms or a substituted or unsubstituted aryl 20 group of 6 to 20 carbonatoms, R¹⁶ to R²⁵ are independently hydrogen or monovalent hydrocarbongroups of 1 to 15 carbon atoms which may contain a hetero atom, R¹⁶ toR²⁵, taken together, may form a ring, and each of R¹⁶ to R²⁵ representsa divalent hydrocarbon group of 1 to 15 carbon atoms which may contain ahetero atom, when they form a ring, or two of R¹⁶ to R25 which areattached to adjoining carbon atoms may bond together directly to form adouble bond.